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Sample records for beta sheet formation

  1. Conformational diversity in prion protein variants influences intermolecular [beta]-sheet formation

    SciTech Connect

    Lee, Seungjoo; Antony, Lizamma; Hartmann, Rune; Knaus, Karen J.; Surewicz, Krystyna; Surewicz, Witold K.; Yee, Vivien C.

    2010-04-19

    A conformational transition of normal cellular prion protein (PrP{sup C}) to its pathogenic form (PrP{sup Sc}) is believed to be a central event in the transmission of the devastating neurological diseases known as spongiform encephalopathies. The common methionine/valine polymorphism at residue 129 in the PrP influences disease susceptibility and phenotype. We report here seven crystal structures of human PrP variants: three of wild-type (WT) PrP containing V129, and four of the familial variants D178N and F198S, containing either M129 or V129. Comparison of these structures with each other and with previously published WT PrP structures containing M129 revealed that only WT PrPs were found to crystallize as domain-swapped dimers or closed monomers; the four mutant PrPs crystallized as non-swapped dimers. Three of the four mutant PrPs aligned to form intermolecular {beta}-sheets. Several regions of structural variability were identified, and analysis of their conformations provides an explanation for the structural features, which can influence the formation and conformation of intermolecular {beta}-sheets involving the M/V129 polymorphic residue.

  2. Liquid Crystal Based Sensor to Detect Beta-Sheet Formation of Peptides

    NASA Astrophysics Data System (ADS)

    Sadati, Monirosadat; Izmitli Apik, Aslin; Abbott, Nicholas L.; de Pablo, Juan J.

    2015-03-01

    Protein aggregation into amyloid fibrils is involved in the progression of Alzheimer's, typeII diabetes and Huntington's diseases. Although larger aggregates remain important for clinical determination, small oligomers are of great interest due to their potentially toxic nature. It is therefore crucial to develop methods that probe the aggregation process at early stages and in the vicinity of biological membranes. Here, we present a simple method that relies on liquid crystalline materials and a Langmuir monolayer at the aqueous-liquid crystal (LC) interface. The approach is based on the LC's specific response to β-sheet structures, which abound in amyloid fibrils. When the system is observed under polarized light, the fibrils formed by amyloidogenic peptides give rise to the formation of elongated and branched structures in the LCs. Moreover, the PolScope measurements prove that the LCs are predominantly aligned along the fibrils when exposed to a β-sheet forming peptide. In contrast, non-amyloidogenic peptides form ellipsoidal domains of irregularly tilted LCs. This method is capable of reporting aggregation at lipid-aqueous interfaces at nanomolar concentrations of the peptide, and much earlier than commonly used fluorescence-based techniques. We thank Prof. Oleg D. Levrentovich and Young-Ki Kim from the Liquid Crystal Institute of Kent State University for the use of their PolScope instrument. This work was partially supported by the Swiss National Science Foundation (P300P2_151342).

  3. Singular points of protein beta-sheets.

    PubMed Central

    Liu, W. M.; Chou, K. C.

    1998-01-01

    Protein beta-sheets can be regarded as surfaces. Two surfaces can be connected along a common edge to form a larger surface, or two edges of a surface can coalesce to form a closed sheet such as a beta-barrel. Singular points are locations where these connections are not perfect. In protein beta-sheets, a singular point is characterized by a residue separating two beta-ladders. In this paper, we study the singular points of protein beta-sheets from the surface topologic viewpoint, summarize our search results from the protein structural data in the Protein Data Bank, and present examples where singular points are near the active sites and may contribute to forming the proper relative positions of catalytic residues. PMID:9827998

  4. Sequence specificity, statistical potentials, and three-dimensional structure prediction with self-correcting distance geometry calculations of beta-sheet formation in proteins.

    PubMed Central

    Zhu, H.; Braun, W.

    1999-01-01

    A statistical analysis of a representative data set of 169 known protein structures was used to analyze the specificity of residue interactions between spatial neighboring strands in beta-sheets. Pairwise potentials were derived from the frequency of residue pairs in nearest contact, second nearest and third nearest contacts across neighboring beta-strands compared to the expected frequency of residue pairs in a random model. A pseudo-energy function based on these statistical pairwise potentials recognized native beta-sheets among possible alternative pairings. The native pairing was found within the three lowest energies in 73% of the cases in the training data set and in 63% of beta-sheets in a test data set of 67 proteins, which were not part of the training set. The energy function was also used to detect tripeptides, which occur frequently in beta-sheets of native proteins. The majority of native partners of tripeptides were distributed in a low energy range. Self-correcting distance geometry (SECODG) calculations using distance constraints sets derived from possible low energy pairing of beta-strands uniquely identified the native pairing of the beta-sheet in pancreatic trypsin inhibitor (BPTI). These results will be useful for predicting the structure of proteins from their amino acid sequence as well as for the design of proteins containing beta-sheets. PMID:10048326

  5. The Promiscuity of [beta]-Strand Pairing Allows for Rational Design of [beta]-Sheet Face Inversion

    SciTech Connect

    Makabe, Koki; Koide, Shohei

    2009-06-17

    Recent studies suggest the dominant role of main-chain H-bond formation in specifying {beta}-sheet topology. Its essentially sequence-independent nature implies a large degree of freedom in designing {beta}-sheet-based nanomaterials. Here we show rational design of {beta}-sheet face inversions by incremental deletions of {beta}-strands from the single-layer {beta}-sheet of Borrelia outer surface protein A. We show that a {beta}-sheet structure can be maintained when a large number of native contacts are removed and that one can design large-scale conformational transitions of a {beta}-sheet such as face inversion by exploiting the promiscuity of strand-strand interactions. High-resolution X-ray crystal structures confirmed the success of the design and supported the importance of main-chain H-bonds in determining {beta}-sheet topology. This work suggests a simple but effective strategy for designing and controlling nanomaterials based on {beta}-rich peptide self-assemblies.

  6. Amyloid Beta Mediates Memory Formation

    ERIC Educational Resources Information Center

    Garcia-Osta, Ana; Alberini, Cristina M.

    2009-01-01

    The amyloid precursor protein (APP) undergoes sequential cleavages to generate various polypeptides, including the amyloid [beta] (1-42) peptide (A[beta][1-42]), which is believed to play a major role in amyloid plaque formation in Alzheimer's disease (AD). Here we provide evidence that, in contrast with its pathological role when accumulated,…

  7. Design and NMR conformational study of a beta-sheet peptide based on Betanova and WW domains.

    PubMed

    Fernández-Escamilla, Ana M; Ventura, Salvador; Serrano, Luis; Jiménez, M Angeles

    2006-10-01

    A good approach to test our current knowledge on formation of protein beta-sheets is de novo protein design. To obtain a three-stranded beta-sheet mini-protein, we have built a series of chimeric peptides by taking as a template a previously designed beta-sheet peptide, Betanova-LLM, and incorporating N- and/or C-terminal extensions taken from WW domains, the smallest natural beta-sheet domain that is stable in absence of disulfide bridges. Some Betanova-LLM strand residues were also substituted by those of a prototype WW domain. The designed peptides were cloned and expressed in Escherichia coli. The ability of the purified peptides to adopt beta-sheet structures was examined by circular dichroism (CD). Then, the peptide showing the highest beta-sheet population according to the CD spectra, named 3SBWW-2, was further investigated by 1H and 13C NMR. Based on NOE and chemical shift data, peptide 3SBWW-2 adopts a well defined three-stranded antiparallel beta-sheet structure with a disordered C-terminal tail. To discern between the contributions to beta-sheet stability of strand residues and the C-terminal extension, the structural behavior of a control peptide with the same strand residues as 3SBWW-2 but lacking the C-terminal extension, named Betanova-LYYL, was also investigated. beta-Sheet stability in these two peptides, in the parent Betanova-LLM and in WW-P, a prototype WW domain, decreased in the order WW-P > 3SBWW-2 > Betanova-LYYL > Betanova-LLM. Conclusions about the contributions to beta-sheet stability were drawn by comparing structural properties of these four peptides.

  8. Evidence for Novel [beta]-Sheet Structures in Iowa Mutant [beta]-Amyloid Fibrils

    SciTech Connect

    Tycko, Robert; Sciarretta, Kimberly L.; Orgel, Joseph P.R.O.; Meredith, Stephen C.

    2009-07-24

    Asp23-to-Asn mutation within the coding sequence of {beta}-amyloid, called the Iowa mutation, is associated with early onset, familial Alzheimer's disease and cerebral amyloid angiopathy, in which patients develop neuritic plaques and massive vascular deposition predominantly of the mutant peptide. We examined the mutant peptide, D23N-A{beta}40, by electron microscopy, X-ray diffraction, and solid-state NMR spectroscopy. D23N-A{beta}40 forms fibrils considerably faster than the wild-type peptide (k = 3.77 x 10{sup -3} min{sup -1} and 1.07 x 10{sup -4} min{sup -1} for D23N-A{beta}40 and the wild-type peptide WT-A{beta}40, respectively) and without a lag phase. Electron microscopy shows that D23N-A{beta}40 forms fibrils with multiple morphologies. X-ray fiber diffraction shows a cross-{beta} pattern, with a sharp reflection at 4.7 {angstrom} and a broad reflection at 9.4 {angstrom}, which is notably smaller than the value for WT-A{beta}40 fibrils (10.4 {angstrom}). Solid-state NMR measurements indicate molecular level polymorphism of the fibrils, with only a minority of D23N-A{beta}40 fibrils containing the in-register, parallel {beta}-sheet structure commonly found in WT-A{beta}40 fibrils and most other amyloid fibrils. Antiparallel {beta}-sheet structures in the majority of fibrils are indicated by measurements of intermolecular distances through 13C-13C and 15N-13C dipole-dipole couplings. An intriguing possibility exists that there is a relationship between the aberrant structure of D23N-A{beta}40 fibrils and the unusual vasculotropic clinical picture in these patients.

  9. Nonlinear current sheet formation in ideal plasmas

    NASA Technical Reports Server (NTRS)

    Voge, A.; Schindler, K.; Otto, A.

    1994-01-01

    We present a numerical study of the formation of current sheets in ideal plasmas. First we confirm the development of singular current sheets in a one-dimensional model. In a second step we extend the analysis to two-dimensional equilibria. Here it is found that the resulting structures are quiet insensitive to the boundary conditions. For the special case of a magnetotail like equilibrium it will be shown that the resulting current distribution provides a possibility to understand the onset of a localized anomalous resistivity from a macroscopic point of view. Furthermore, the resulting structures provide an explanation for the dramatic decrease of the thickness of the current sheet in the magnetotail prior to the onset of geomagnetic substorms.

  10. Tape-casting technique can prepare beta-TCP sheets with uniform thickness and flexibility.

    PubMed

    Tanimoto, Yasuhiro; Hayakawa, Tohru; Nemoto, Kimiya

    2005-04-01

    The objective of this study is to propose a new fabrication technology for bone substitutes. In this study, a tape-casting method was used to prepare flexible beta-tricalcium phosphate (beta-TCP) sheets. A beta-TCP slurry containing a binder and plasticizer was used in a doctor blade system. The beta-TCP sheet obtained by this tape-casting method was highly flexible, enabling twisting and free-form shaping. The beta-TCP sheet was approximately 0.21 mm thick. X-ray diffraction and Fourier transform infrared spectrometry revealed that the structure of the beta-TCP component in the sheet is the same as that of the original beta-TCP powder. Observation by field-emission scanning electron microscopy showed that the beta-TCP sheet had a flat, microgranular surface. During the early stages, the tensile stress-strain curves of the beta-TCP sheet showed a nonlinear behavior until reaching the point of final fracture. This result was derived from the ductile property of the prepared beta-TCP sheet. In conclusion, a flexible beta-TCP sheet was easily prepared using a tape-casting technique. Fabrication using tape casting offers the advantages of enabling the preparation of ceramic sheets with precise thickness and not requiring expensive fabrication facilities.

  11. Formation of Sprays From Conical Liquid Sheets

    NASA Technical Reports Server (NTRS)

    Peck, Bill; Mansour, N. N.; Koga, Dennis (Technical Monitor)

    1999-01-01

    Our objective is to predict droplet size distributions created by fuel injector nozzles in Jet turbines. These results will be used to determine the initial conditions for numerical simulations of the combustion process in gas turbine combustors. To predict the droplet size distribution, we are currently constructing a numerical model to understand the instability and breakup of thin conical liquid sheets. This geometry serves as a simplified model of the liquid jet emerging from a real nozzle. The physics of this process is difficult to study experimentally as the time and length scales are very short. From existing photographic data, it does seem clear that three-dimensional effects such as the formation of streamwise ligaments and the pulling back of the sheet at its edges under the action of surface tension are important.

  12. Role of Polyalanine Domains in -Sheet Formation in Spider Silk Block Copolymers

    SciTech Connect

    Rabotyagova, O.; Cebe, P; Kaplan, D

    2010-01-01

    Genetically engineered spider silk-like block copolymers were studied to determine the influence of polyalanine domain size on secondary structure. The role of polyalanine block distribution on {beta}-sheet formation was explored using FT-IR and WAXS. The number of polyalanine blocks had a direct effect on the formation of crystalline {beta}-sheets, reflected in the change in crystallinity index as the blocks of polyalanines increased. WAXS analysis confirmed the crystalline nature of the sample with the largest number of polyalanine blocks. This approach provides a platform for further exploration of the role of specific amino acid chemistries in regulating the assembly of {beta}-sheet secondary structures, leading to options to regulate material properties through manipulation of this key component in spider silks.

  13. Current Sheets Formation in Planetary Magnetotail

    NASA Astrophysics Data System (ADS)

    Otto, Antonius; Hsieh, Min-Shiu; Hall, Fred

    2015-01-01

    Current sheet (CS) formation and thinning are common and fundamentally important processes in space and laboratory plasmas. CSs are always present in the interaction of plasmas of different origins and their presence is a necessary requirement for the onset of magnetic reconnection. The thinning of the near-Earth CS is highly important because it represents a major reconfiguration of the magnetotail from a mostly dipolar to a highly stretched magnetic field, which determines the conditions for substorm onset. Processes that can alter flux tube entropy include magnetic reconnection, energy loss into the ionosphere, gradients in energetic particle drifts, or kinetic processes that change the pressure or its isotropy. The plasma entropy increases with radial distance in the Jovian magnetosphere, which requires non-adiabatic heating during the outward plasma transport. The formation of CSs represents a fundamentally important and not-well-understood problem of planetary magnetotails and magnetodiscs.

  14. A recipe for designing water-soluble, beta-sheet-forming peptides.

    PubMed Central

    Mayo, K. H.; Ilyina, E.; Park, H.

    1996-01-01

    Based on observations of solubility and folding properties of peptide 33-mers derived from the beta-sheet domains of platelet factor-4 (PF4), interleukin-8 (IL-8), and growth related protein (Gro-alpha), as well as other beta-sheet-forming peptides, general guidelines have been developed to aid in the design of water soluble, self-association-induced beta-sheet-forming peptides. CD, 1H-NMR, and pulsed field gradient NMR self-diffusion measurements have been used to assess the degree of folding and state of aggregation. PF4 peptide forms native-like beta-sheet tetramers and is sparingly soluble above pH 6. IL-8 peptide is insoluble between pH 4.5 and pH 7.5, yet forms stable, native-like beta-sheet dimers at higher pH. Gro-alpha peptide is soluble at all pH values, yet displays no discernable beta-sheet structure even when diffusion data indicate dimer-tetramer aggregation. A recipe used in the de novo design of water-soluble beta-sheet-forming peptides calls for the peptide to contain 40-50% hydrophobic residues, usually aliphatic ones (I, L, V, A, M) (appropriately paired and mostly but not always alternating with polar residues in the sheet sequence), a positively charged (K, R) to negatively charged (E, D) residue ratio between 4/2 and 6/2, and a noncharged polar residue (N, Q, T, S) composition of about 20% or less. Results on four de novo designed, 33-residue peptides are presented supporting this approach. Under near physiologic conditions, all four peptides are soluble, form beta-sheet structures to varying degrees, and self-associate. One peptide folds as a stable, compact beta-sheet tetramer, whereas the others are transient beta-sheet-containing aggregates. PMID:8819163

  15. Cooperative deformation of hydrogen bonds in beta-strands and beta-sheet nanocrystals

    NASA Astrophysics Data System (ADS)

    Qin, Zhao; Buehler, Markus J.

    2010-12-01

    Beta-sheet protein domains are stabilized by weak hydrogen bonds, yet materials such as silk—whose ultimate tensile strength is controlled primarily by this secondary structure—can exceed the ultimate tensile strength of steel. Earlier work has suggested that this is because hydrogen bonds deform cooperatively within small protein domains to reach the maximum strength. Here we study the atomistic mechanism of this concerted deformation mechanism by applying an elastic structural model, used to solve the deformation field of the chemical bonds in beta-sheet nanostructures under stretching and thereby identify the number of hydrogen bonds that deform cooperatively. Through this analysis, we predict the optimal beta-strand and beta-sheet nanocrystal size associated with reaching the maximum usage of hydrogen bonds under loading applied per unit material volume. Our results, albeit based on a simple model and analytical equations, quantitatively agree with results based on experimental and molecular-dynamics studies and provide physical insight into the underlying molecular mechanisms of weak bond cooperativity. A comparison with the size of hydrogen bond clusters in biology reveals excellent agreement with the cluster sizes predicted by our analysis, suggesting that perhaps the confinement of hydrogen bonds into nanoscale elements is a universal biological design paradigm that turns weakness to strength. The parameters used in this study could be modified and applied to other protein and polymer structures, which imply potential applications of our model in understanding the physics of deformation and failure in a broader range of biological and polymer materials, as well as in de novo biomaterial design.

  16. Propagating structure of alzheimer's {beta}-amyloid is parallel {beta}-sheet with residues in exact register.

    SciTech Connect

    Benzinger, T. L. S.; Gregory, D. M.; Burkoth, T. S.; Miller-Auer, H.; Lynn, D. G.; Botto, R. E.; Meredith, S. C.; Chemistry; Univ. of Chicago

    1998-11-10

    The pathognomonic plaques of Alzheimer's disease are composed primarily of the 39- to 43-aa {beta}-amyloid (A{beta}) peptide. Crosslinking of A{beta} peptides by tissue transglutaminase (tTg) indicates that Gln15 of one peptide is proximate to Lys16 of another in aggregated A{beta}. Here we report how the fibril structure is resolved by mapping interstrand distances in this core region of the A{beta} peptide chain with solid-state NMR. Isotopic substitution provides the source points for measuring distances in aggregated A{beta}. Peptides containing a single carbonyl 13C label at Gln15, Lys16, Leu17, or Val18 were synthesized and evaluated by NMR dipolar recoupling methods for the measurement of interpeptide distances to a resolution of 0.2 Angstrom. Analysis of these data establish that this central core of A{beta} consists of a parallel {beta}-sheet structure in which identical residues on adjacent chains are aligned directly, i.e., in register. Our data, in conjunction with existing structural data, establish that the A{beta} fibril is a hydrogen-bonded, parallel {beta}-sheet defining the long axis of the A{beta} fibril propagation.

  17. Formation of thin bifurcated current sheets by quasisteady compression

    SciTech Connect

    Schindler, Karl; Hesse, Michael

    2008-04-15

    Thin current sheets with half-widths in the range of about 10 or less ion inertial lengths (or ion gyroradii) have been identified as the sites of important dynamical phenomena in space plasmas. Recent space observations established that thin current sheets often have a bifurcated (double-peaked) current density. Earlier suggestions of possible bifurcation mechanisms are based on the presence of microfluctuations, magnetic reconnection, or a normal magnetic field component or assumed simplified models of adiabatic dynamics. Despite these efforts, the cause (or causes) of the formation of thin bifurcated current sheets and the conditions under which they form have remained unclear. In this paper, we identify quasisteady compression of a plane, initially wide collisionless current sheet as an effective physical mechanism for the formation of thin bifurcated current sheets. Our main tool is electromagnetic particle simulation. The initial sheet has a singly peaked current and a half-width that is five times larger than the ion inertial length. This sheet is quasisteadily compressed by external forces. A three-scale structure develops and the current bifurcates during compression. It is shown that the bifurcation, pressure anisotropy, and other major properties of the embedded current sheet can be understood in terms of basic physical principles, such as electric field shielding and momentum conservation. Sufficient conditions for bifurcation of symmetric current sheets are presented. They suggest that bifurcation must generally occur by quasisteady compression if the (singly peaked) initial current sheet is sufficiently wide.

  18. Misfolded amyloid ion channels present mobile beta-sheet subunits in contrast to conventional ion channels.

    PubMed

    Jang, Hyunbum; Arce, Fernando Teran; Capone, Ricardo; Ramachandran, Srinivasan; Lal, Ratnesh; Nussinov, Ruth

    2009-12-02

    In Alzheimer's disease, calcium permeability through cellular membranes appears to underlie neuronal cell death. It is increasingly accepted that calcium permeability involves toxic ion channels. We modeled Alzheimer's disease ion channels of different sizes (12-mer to 36-mer) in the lipid bilayer using molecular dynamics simulations. Our Abeta channels consist of the solid-state NMR-based U-shaped beta-strand-turn-beta-strand motif. In the simulations we obtain ion-permeable channels whose subunit morphologies and shapes are consistent with electron microscopy/atomic force microscopy. In agreement with imaged channels, the simulations indicate that beta-sheet channels break into loosely associated mobile beta-sheet subunits. The preferred channel sizes (16- to 24-mer) are compatible with electron microscopy/atomic force microscopy-derived dimensions. Mobile subunits were also observed for beta-sheet channels formed by cytolytic PG-1 beta-hairpins. The emerging picture from our large-scale simulations is that toxic ion channels formed by beta-sheets spontaneously break into loosely interacting dynamic units that associate and dissociate leading to toxic ionic flux. This sharply contrasts intact conventional gated ion channels that consist of tightly interacting alpha-helices that robustly prevent ion leakage, rather than hydrogen-bonded beta-strands. The simulations suggest why conventional gated channels evolved to consist of interacting alpha-helices rather than hydrogen-bonded beta-strands that tend to break in fluidic bilayers. Nature designs folded channels but not misfolded toxic channels.

  19. Formation of silicon sheet on a rotating substrate.

    PubMed

    Lee, Jaewoo; Lee, Changbum; Kim, Joonsoo; Jang, Bo-Yun; Ahn, Youngsoo; Yoon, Wooyoung

    2012-04-01

    A spin casting process to fabricate polycrystalline silicon sheets for use as solar cell wafers is presented and the parameters that control the sheet thickness are investigated. The computational model for the spin casting is proposed in order to understand the melt flow and solidification behaviors in the mold. The effect of the rotating speed of the mold and substrate morphology on the silicon sheets is studied via computer simulations, and the simulation results are compared with the experimental results. The numerical study of the fluidity and solidification behavior of the silicon predicted that the formation of rectangular sheets via spin casting is feasible, and the subsequent experiment confirmed this prediction. Using a square mold, rectangular silicon sheets can be produced under appropriate experimental conditions. Microstructural analyses verified the presence of long columnar structures on the sheets.

  20. Conversion of non-fibrillar {beta}-sheet oligomers into amyloid fibrils in Alzheimer's disease amyloid peptide aggregation

    SciTech Connect

    Benseny-Cases, Nuria; Cocera, Mercedes; Cladera, Josep

    2007-10-05

    A{beta}(1-40) is one of the main components of the fibrils found in amyloid plaques, a hallmark of brains affected by Alzheimer's disease. It is known that prior to the formation of amyloid fibrils in which the peptide adopts a well-ordered intermolecular {beta}-sheet structure, peptide monomers associate forming low and high molecular weight oligomers. These oligomers have been previously described in electron microscopy, AFM, and exclusion chromatography studies. Their specific secondary structures however, have not yet been well established. A major problem when comparing aggregation and secondary structure determinations in concentration-dependent processes such as amyloid aggregation is the different concentration range required in each type of experiment. In the present study we used the dye Thioflavin T (ThT), Fourier-transform infrared spectroscopy, and electron microscopy in order to structurally characterize the different aggregated species which form during the A{beta}(1-40) fibril formation process. A unique sample containing 90 {mu}M peptide was used. The results show that oligomeric species which form during the lag phase of the aggregation kinetics are a mixture of unordered, helical, and intermolecular non-fibrillar {beta}-structures. The number of oligomers and the amount of non-fibrillar {beta}-structures grows throughout the lag phase and during the elongation phase these non-fibrillar {beta}-structures are transformed into fibrillar (amyloid) {beta}-structures, formed by association of high molecular weight intermediates.

  1. Formation of current sheets in magnetic reconnection

    SciTech Connect

    Boozer, Allen H.

    2014-07-15

    An ideal evolution of magnetic fields in three spatial dimensions tends to cause neighboring field lines to increase their separation exponentially with distance ℓ along the lines, δ(ℓ)=δ(0)e{sup σ(ℓ)}. The non-ideal effects required to break magnetic field line connections scale as e{sup −σ}, so the breaking of connections is inevitable for σ sufficiently large—even though the current density need nowhere be large. When the changes in field line connections occur rapidly compared to an Alfvén transit time, the constancy of j{sub ||}/B along the magnetic field required for a force-free equilibrium is broken in the region where the change occurs, and an Alfvénic relaxation of j{sub ||}/B occurs. Independent of the original spatial distribution of j{sub ||}/B, the evolution is into a sheet current, which is stretched by a factor e{sup σ} in width and contracted by a factor e{sup σ} in thickness with the current density j{sub ||} increasing as e{sup σ}. The dissipation of these sheet currents and their associated vorticity sheets appears to be the mechanism for transferring energy from a reconnecting magnetic field to a plasma. Harris sheets, which are used in models of magnetic reconnection, are shown to break up in the direction of current flow when they have a finite width and are in a plasma in force equilibrium. The dependence of the longterm nature of magnetic reconnection in systems driven by footpoint motion can be studied in a model that allows qualitative variation in the nature of that motion: slow or fast motion compared to the Alfvén transit time and the neighboring footpoints either exponentially separating in time or not.

  2. Numerical simulation of current sheet formation in a quasiseparatrix layer using adaptive mesh refinement

    SciTech Connect

    Effenberger, Frederic; Thust, Kay; Grauer, Rainer; Dreher, Juergen; Arnold, Lukas

    2011-03-15

    The formation of a thin current sheet in a magnetic quasiseparatrix layer (QSL) is investigated by means of numerical simulation using a simplified ideal, low-{beta}, MHD model. The initial configuration and driving boundary conditions are relevant to phenomena observed in the solar corona and were studied earlier by Aulanier et al. [Astron. Astrophys. 444, 961 (2005)]. In extension to that work, we use the technique of adaptive mesh refinement (AMR) to significantly enhance the local spatial resolution of the current sheet during its formation, which enables us to follow the evolution into a later stage. Our simulations are in good agreement with the results of Aulanier et al. up to the calculated time in that work. In a later phase, we observe a basically unarrested collapse of the sheet to length scales that are more than one order of magnitude smaller than those reported earlier. The current density attains correspondingly larger maximum values within the sheet. During this thinning process, which is finally limited by lack of resolution even in the AMR studies, the current sheet moves upward, following a global expansion of the magnetic structure during the quasistatic evolution. The sheet is locally one-dimensional and the plasma flow in its vicinity, when transformed into a comoving frame, qualitatively resembles a stagnation point flow. In conclusion, our simulations support the idea that extremely high current densities are generated in the vicinities of QSLs as a response to external perturbations, with no sign of saturation.

  3. Rationally designed mutations convert de novo amyloid-like fibrils into monomeric beta-sheet proteins.

    PubMed

    Wang, Weixun; Hecht, Michael H

    2002-03-05

    Amyloid fibrils are associated with a variety of neurodegenerative maladies including Alzheimer's disease and the prion diseases. The structures of amyloid fibrils are composed of beta-strands oriented orthogonal to the fibril axis ("cross beta" structure). We previously reported the design and characterization of a combinatorial library of de novo beta-sheet proteins that self-assemble into fibrillar structures resembling amyloid. The libraries were designed by using a "binary code" strategy, in which the locations of polar and nonpolar residues are specified explicitly, but the identities of these residues are not specified and are varied combinatorially. The initial libraries were designed to encode proteins containing amphiphilic beta-strands separated by reverse turns. Each beta-strand was designed to be seven residues long, with polar (open circle) and nonpolar (shaded circle) amino acids arranged with an alternating periodicity ([see text]). The initial design specified the identical polar/nonpolar pattern for all of the beta-strands; no strand was explicitly designated to form the edges of the resulting beta-sheets. With all beta-strands preferring to occupy interior (as opposed to edge) locations, intermolecular oligomerization was favored, and the proteins assembled into amyloid-like fibrils. To assess whether explicit design of edge-favoring strands might tip the balance in favor of monomeric beta-sheet proteins, we have now redesigned the first and/or last beta-strands of several sequences from the original library. In the redesigned beta-strands, the binary pattern is changed from [see text] (K denotes lysine). The presence of a lysine on the nonpolar face of a beta-strand should disfavor fibrillar structures because such structures would bury an uncompensated charge. The nonpolar right arrow lysine mutations, therefore, would be expected to favor monomeric structures in which the [see text] sequences form edge strands with the charged lysine side

  4. Conversion of non-fibrillar beta-sheet oligomers into amyloid fibrils in Alzheimer's disease amyloid peptide aggregation.

    PubMed

    Benseny-Cases, Núria; Cócera, Mercedes; Cladera, Josep

    2007-10-05

    Abeta(1-40) is one of the main components of the fibrils found in amyloid plaques, a hallmark of brains affected by Alzheimer's disease. It is known that prior to the formation of amyloid fibrils in which the peptide adopts a well-ordered intermolecular beta-sheet structure, peptide monomers associate forming low and high molecular weight oligomers. These oligomers have been previously described in electron microscopy, AFM, and exclusion chromatography studies. Their specific secondary structures however, have not yet been well established. A major problem when comparing aggregation and secondary structure determinations in concentration-dependent processes such as amyloid aggregation is the different concentration range required in each type of experiment. In the present study we used the dye Thioflavin T (ThT), Fourier-transform infrared spectroscopy, and electron microscopy in order to structurally characterize the different aggregated species which form during the Abeta(1-40) fibril formation process. A unique sample containing 90microM peptide was used. The results show that oligomeric species which form during the lag phase of the aggregation kinetics are a mixture of unordered, helical, and intermolecular non-fibrillar beta-structures. The number of oligomers and the amount of non-fibrillar beta-structures grows throughout the lag phase and during the elongation phase these non-fibrillar beta-structures are transformed into fibrillar (amyloid) beta-structures, formed by association of high molecular weight intermediates.

  5. Flanking Polyproline Sequences Inhibit [beta]-Sheet Structure in Polyglutamine Segments by Inducing PPII-like Helix Structure

    SciTech Connect

    Darnell, Gregory; Orgel, Joseph P.R.O.; Pahl, Reinhard; Meredith, Stephen C.

    2008-06-24

    Polyglutamine (poly(Q)) expansion is associated with protein aggregation into {beta}-sheet amyloid fibrils and neuronal cytotoxicity. In the mutant poly(Q) protein huntingtin, associated with Huntington's disease, both aggregation and cytotoxicity may be abrogated by a polyproline (poly(P)) domain flanking the C terminus of the poly(Q) region. To understand structural changes that may occur with the addition of the poly(P) sequence, we synthesized poly(Q) peptides with 3-15 glutamine residues and a corresponding set of poly(Q) peptides flanked on the C terminus by 11 proline residues (poly(Q)-poly(P)), as occurs in the huntingtin sequence. The shorter soluble poly(Q) peptides (three or six glutamine residues) showed polyproline type II-like (PPII)-like helix conformation when examined by circular dichroism spectroscopy and were monomers as judged by size-exclusion chromatography (SEC), while the longer poly(Q) peptides (nine or 15 glutamine residues) showed a {beta}-sheet conformation by CD and defined oligomers by SEC. Soluble poly(Q)-poly(P) peptides showed PPII-like content but SEC showed poorly defined, overlapping oligomeric peaks, and as judged by CD these peptides retained significant PPII-like structure with increasing poly(Q) length. More importantly, addition of the poly(P) domain increased the threshold for fibril formation to {approx} 15 glutamine residues. X-ray diffraction, electron microscopy, and film CD showed that, while poly(Q) peptides with {ge} 6 glutamine residues formed {beta}-sheet-rich fibrils, only the longest poly(Q)-poly(P) peptide (15 glutamine residues) did so. From these and other observations, we propose that poly(Q) domains exist in a 'tug-of-war' between two conformations, a PPII-like helix and a {beta}-sheet, while the poly(P) domain is conformationally constrained into a proline type II helix (PPII). Addition of poly(P) to the C terminus of a poly(Q) domain induces a PPII-like structure, which opposes the aggregation-prone {beta}-sheet

  6. Plasmoid formation in current sheet with finite normal magnetic component.

    PubMed

    Zhu, P; Raeder, J

    2013-06-07

    Current sheet configurations in natural and laboratory plasmas are often accompanied by a finite normal magnetic component that is known to stabilize the two-dimensional resistive tearing instability in the high Lundquist number regime. Recent magnetohydrodynamic simulations indicate that the nonlinear development of ballooning instability is able to induce the formation of X lines and plasmoids in a generalized Harris sheet with a finite normal magnetic component in the high Lundquist number regime where the linear two-dimensional resistive tearing mode is stable.

  7. A minimalist approach toward protein recognition by epitope transfer from functionally evolved beta-sheet surfaces.

    PubMed

    Rajagopal, Srivats; Meyer, Scott C; Goldman, Aaron; Zhou, Min; Ghosh, Indraneel

    2006-11-08

    New approaches for identifying small molecules that specifically target protein surfaces as opposed to active site clefts are of much current interest. Toward this goal, we describe a three-step methodology: in step one, we target a protein of interest by directed evolution of a small beta-sheet scaffold; in step two, we identify residues on the scaffold that are implicated in binding; and in step three, we transfer the chemical information from the beta-sheet to a small molecule mimic. As a case study, we targeted the proteolytic enzyme thrombin, involved in blood coagulation, utilizing a library of beta-sheet epitopes displayed on phage that were previously selected for conservation of structure. We found that the thrombin-binding, beta-sheet displaying mini-proteins retained their structure and stability while inhibiting thrombin at low micromolar inhibition constants. A conserved dityrosine recognition motif separated by 9.2 A was found to be common among the mini-protein inhibitors and was further verified by alanine scanning. A molecule containing two tyrosine residues separated by a linker that matched the spacing on the beta-sheet scaffold inhibited thrombin, whereas a similar dityrosine molecule separated by a shorter 6 A linker could not. Moreover, kinetic analysis revealed that both the mini-protein as well as its minimalist mimic with only two functional residues exhibited noncompetitive inhibition of thrombin. Thus, this reductionist approach affords a simple methodology for transferring information from structured protein scaffolds to yield small molecule leads for targeting protein surfaces with novel mechanisms of action.

  8. Prion protein helix1 promotes aggregation but is not converted into beta-sheet.

    PubMed

    Watzlawik, Jens; Skora, Lukasz; Frense, Dieter; Griesinger, Christian; Zweckstetter, Markus; Schulz-Schaeffer, Walter J; Kramer, Michael L

    2006-10-06

    Prion diseases are caused by the aggregation of the native alpha-helical prion protein PrP(C) into its pathological beta-sheet-rich isoform PrP(Sc). In current models of PrP(Sc), helix1 is assumed to be preferentially converted into beta-sheet during aggregation of PrP(C). This was supported by the NMR structure of PrP(C) since, in contrast to the isolated helix1, helix2 and helix3 are connected by a small loop and are additionally stabilized by an interhelical disulfide bond. However, helix1 is extremely hydrophilic and has a high helix propensity. This prompted us to investigate the role of helix1 in prion aggregation using humPrP(23-159) including helix1 (144-156) compared with the C-terminal-truncated isoform humPrP(23-144) corresponding to the pathological human stop mutations Q160Stop and Y145Stop, respectively. Most unexpectedly, humPrP(23-159) aggregated significantly faster compared with the truncated fragment humPrP(23-144), clearly demonstrating that helix1 is involved in the aggregation process. However, helix1 is not resistant to digestion with proteinase K in fibrillar humPrP(23-159), suggesting that helix1 is not converted to beta-sheet. This is confirmed by Fourier transformation infrared spectroscopy since there is almost no difference in beta-sheet content of humPrP(23-159) fibrils compared with humPrP(23-144). In conclusion, we provide strong direct evidence that in contrast to earlier assumptions helix1 is not converted into beta-sheet during aggregation of PrP(C) to PrP(Sc).

  9. Laminin-521 Promotes Rat Bone Marrow Mesenchymal Stem Cell Sheet Formation on Light-Induced Cell Sheet Technology

    PubMed Central

    2017-01-01

    Rat bone marrow mesenchymal stem cell sheets (rBMSC sheets) are attractive for cell-based tissue engineering. However, methods of culturing rBMSC sheets are critically limited. In order to obtain intact rBMSC sheets, a light-induced cell sheet method was used in this study. TiO2 nanodot films were coated with (TL) or without (TN) laminin-521. We investigated the effects of laminin-521 on rBMSCs during cell sheet culturing. The fabricated rBMSC sheets were subsequently assessed to study cell sheet viability, reattachment ability, cell sheet thickness, collagen type I deposition, and multilineage potential. The results showed that laminin-521 could promote the formation of rBMSC sheets with good viability under hyperconfluent conditions. Cell sheet thickness increased from an initial 26.7 ± 1.5 μm (day 5) up to 47.7 ± 3.0 μm (day 10). Moreover, rBMSC sheets maintained their potential of osteogenic, adipogenic, and chondrogenic differentiation. This study provides a new strategy to obtain rBMSC sheets using light-induced cell sheet technology. PMID:28164129

  10. Captides: rigid junctions between beta sheets and small molecules.

    PubMed

    Kier, Brandon L; Andersen, Niels H

    2014-09-01

    An extensive series of covalently linked small molecule-peptide adducts based on a terminally capped-beta hairpin motif is reported. The constructs can be prepared by standard solid-phase Fmoc chemistry with one to four peptide chains linked to small molecule hubs bearing carboxylic acid moieties. The key feature of interest is the precise, buried environment of the small molecule, and its rigid orientation relative to one or more short but fully structured peptide chain(s). Most of this study employs a minimalist nine residue 'captide', a capped β-turn, but we illustrate general applicability to peptides which can terminate in a beta strand. The non-peptide portion of these adducts can include nearly any molecule bearing one or more carboxylic acid groups. Fold-dependent rigidity sets this strategy apart from the currently available bioconjugation methods, which typically engender significant flexibility between peptide and tag. Applications to catalyst enhancement, drug design, higher-order assembly, and FRET calibration rulers are discussed.

  11. Captides: Rigid Junctions between Beta Sheets and Small Molecules

    PubMed Central

    Kier, Brandon L.; Andersen, Niels H.

    2014-01-01

    An extensive series of covalently linked small molecule-peptide adducts based on a terminally capped beta hairpin motif is reported. The constructs can be prepared by standard solid-phase fmoc chemistry with 1 to 4 peptide chains linked to small molecule hubs bearing carboxylic acid moieties. The key feature of interest is the precise, buried environment of the small molecule, and its rigid orientation relative to one or more short, but fully structured peptide chain(s). Most of this study employs a minimalist 9 residue “captide”, a capped β-turn, but we illustrate general applicability to peptides which can terminate in a beta strand. The non-peptide portion of these adducts can include nearly any molecule bearing one or more carboxylic acid groups. Fold-dependent rigidity sets this strategy apart from currently available bioconjugation methods, which typically engender significant flexibility between peptide and tag. Applications to catalyst enhancement, drug design, higher-order assembly, and FRET calibration rulers are discussed. PMID:24909552

  12. How stable is a collagen triple helix? An ab initio study on various collagen and beta-sheet forming sequences.

    PubMed

    Pálfi, Villo K; Perczel, András

    2008-07-15

    Collagen forms the well characterized triple helical secondary structure, stabilized by interchain H-bonds. Here we have investigated the stability of fully optimized collagen triple helices and beta-pleated sheets by using first principles (ab initio and DFT) calculations so as to determine the secondary structure preference depending on the amino acid composition. Models composed of a total of 18 amino acid residues were studied at six different amino acid compositions: (i) L-alanine only, (ii) glycine only, (iii) L-alanines and glycine, (iv) L-alanines and D-alanine, (v) L-prolines with glycine, (vi) L-proline, L-hydroxyproline, and glycine. The last two, v and vi, were designed to mimic the core part of collagen. Furthermore, ii, iii, and iv model the binding and/or recognition sites of collagen. Finally, i models the G-->A replacement, rare in collagen. All calculated structures show great resemblance to those determined by X-ray crystallography. Calculated triple helix formation affinities correlate well with experimentally determined stabilities derived from melting point (T(m)) data of different collagen models. The stabilization energy of a collagen triple helical structure over that of a beta-pleated sheet is 2.1 kcal mol(-1) per triplet for the [(-Pro-Hyp-Gly-)(2)](3) collagen peptide. This changes to 4.8 kcal mol(-1) per triplet of destabilization energy for the [(-Ala-Ala-Gly-)(2)](3) sequence, known to be disfavored in collagen. The present study proves that by using first principles methods for calculating stabilities of supramolecular complexes, such as collagen and beta-pleated sheets, one can obtain stability data in full agreement with experimental observations, which envisage the applicability of QM in molecular design.

  13. Thermally Induced Alpha-Helix to Beta-Sheet Transition in Regenerated Silk Fibers and Films

    SciTech Connect

    Drummy,L.; Phillips, D.; Stone, M.; Farmer, B.; Naik, R.

    2005-01-01

    The structure of thin films cast from regenerated solutions of Bombyx mori cocoon silk in hexafluoroisopropyl alcohol (HFIP) was studied by synchrotron X-ray diffraction during heating. A solid-state conformational transition from an alpha-helical structure to the well-known beta-sheet silk II structure occurred at a temperature of approximately 140 degrees C. The transition appeared to be homogeneous, as both phases do not coexist within the resolution of the current study. Modulated differential scanning calorimetry (DSC) of the films showed an endothermic melting peak followed by an exothermic crystallization peak, both occurring near 140 degrees C. Oriented fibers were also produced that displayed this helical molecular conformation. Subsequent heating above the structural transition temperature produced oriented beta-sheet fibers very similar in structure to B. mori cocoon fibers. Heat treatment of silk films at temperatures well below their degradation temperature offers a controllable route to materials with well-defined structures and mechanical behavior.

  14. Reduction of burn scar formation by halofuginone-eluting silicone gel sheets: a controlled study on nude mice.

    PubMed

    Zeplin, Philip H

    2012-03-01

    Burn scar formations can cause disfiguration and loss of dermal function. The purpose of this study was to examine whether application of modified silicone gel sheets with an antifibrotic drug halofuginone-eluting hybrid surface produce an effect on scar development. There were a total of 2 animal groups. The athymic nude mice (nu/nu) of both groups underwent transplantation of full-thickness human skin grafts onto their backs and setting of partial thickness burn injury. The status of local scar development was observed over a period of 3 months after the application of silicone gel sheets and also after application of surface-modified halofuginone-eluting silicone gel sheets. Subsequently, via real-time polymerase chain reaction, the cDNA levels from key mediators of scar formation (transforming growth factor beta, COL1A1, connective tissue growth factor, fibroblast growth factor 2, matrix metalloproteinase 2, matrix metalloproteinase 9) were established and statistically evaluated. In comparison with uncoated silicone gel sheets, the application of halofuginone-eluting silicone gel sheets lead to a significant difference in gene expression activity in scar tissue. Halofuginone-eluting hybrid surface silicone gel sheets significantly increase the antiscarring effect of adhesive silicone gel sheets by deceleration and downregulation of scar development by normalization of the expression activity.

  15. Alpha-helical, but not beta-sheet, propensity of proline is determined by peptide environment.

    PubMed

    Li, S C; Goto, N K; Williams, K A; Deber, C M

    1996-06-25

    Proline is established as a potent breaker of both alpha-helical and beta-sheet structures in soluble (globular) proteins. Thus, the frequent occurrence of the Pro residue in the putative transmembrane helices of integral membrane proteins, particularly transport proteins, presents a structural dilemma. We propose that this phenomenon results from the fact that the structural propensity of a given amino acid may be altered to conform to changes imposed by molecular environment. To test this hypothesis on proline, we synthesized model peptides of generic sequence H2N-(Ser-LyS)2-Ala- Leu-Z-Ala-Leu-Z-Trp-Ala-Leu-Z-(Lys-Ser)3-OH (Z = Ala and/or Pro). Peptide conformations were analyzed by circular dichroism spectroscopy in aqueous buffer, SDS, lysophosphatidylglycerol micelles, and organic solvents (methanol, trifluoroethanol, and 2-propanol). The helical propensity of Pro was found to be greatly enhanced in the membrane-mimetic environments of both lipid micelles and organic solvents. Proline was found to stabilize the alpha-helical conformation relative to Ala at elevated temperatures in 2-propanol, an observation that argues against the doctrine that Pro is the most potent alpha-helix breaker as established in aqueous media. Parallel studies in deoxycholate micelles of the temperature-induced conformational transitions of the single-spanning membrane bacteriophage IKe major coat protein, in which the Pro-containing wild type was compared with Pro30 --> Ala mutant, Pro was found to protect the helix, but disrupt the beta-sheet structure as effectively as it does to model peptides in water. The intrinsic capacity of Pro to disrupt beta-sheets was further reflected in a survey of porins where Pro was found to be selectively excluded from the core of membrane-spanning beta-sheet barrels. The overall data provide a rationale for predicting and understanding the structural consequences when Pro occurs in the context of a membrane.

  16. Alpha-helical, but not beta-sheet, propensity of proline is determined by peptide environment.

    PubMed Central

    Li, S C; Goto, N K; Williams, K A; Deber, C M

    1996-01-01

    Proline is established as a potent breaker of both alpha-helical and beta-sheet structures in soluble (globular) proteins. Thus, the frequent occurrence of the Pro residue in the putative transmembrane helices of integral membrane proteins, particularly transport proteins, presents a structural dilemma. We propose that this phenomenon results from the fact that the structural propensity of a given amino acid may be altered to conform to changes imposed by molecular environment. To test this hypothesis on proline, we synthesized model peptides of generic sequence H2N-(Ser-LyS)2-Ala- Leu-Z-Ala-Leu-Z-Trp-Ala-Leu-Z-(Lys-Ser)3-OH (Z = Ala and/or Pro). Peptide conformations were analyzed by circular dichroism spectroscopy in aqueous buffer, SDS, lysophosphatidylglycerol micelles, and organic solvents (methanol, trifluoroethanol, and 2-propanol). The helical propensity of Pro was found to be greatly enhanced in the membrane-mimetic environments of both lipid micelles and organic solvents. Proline was found to stabilize the alpha-helical conformation relative to Ala at elevated temperatures in 2-propanol, an observation that argues against the doctrine that Pro is the most potent alpha-helix breaker as established in aqueous media. Parallel studies in deoxycholate micelles of the temperature-induced conformational transitions of the single-spanning membrane bacteriophage IKe major coat protein, in which the Pro-containing wild type was compared with Pro30 --> Ala mutant, Pro was found to protect the helix, but disrupt the beta-sheet structure as effectively as it does to model peptides in water. The intrinsic capacity of Pro to disrupt beta-sheets was further reflected in a survey of porins where Pro was found to be selectively excluded from the core of membrane-spanning beta-sheet barrels. The overall data provide a rationale for predicting and understanding the structural consequences when Pro occurs in the context of a membrane. PMID:8692877

  17. Current Sheets Formation and Relaxation of Coronal Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Rappazzo, A. F.

    2013-12-01

    We investigate the relaxation of magnetic fields in closed regions of solar and stellar coronae, extending to further topologies our previous work (Rappazzo, A.F. & Parker, E.N., ApJL, 773, L2 (2013)). The dynamical evolution is integrated with the equations of reduced magnetohydrodynamics (RMHD) apt to model a plasma embedded in a strong guide field B0 extended along the axial direction, where the dynamical field is the orthogonal component b. Dissipative and ideal simulations are carried out in Cartesian geometry: magnetic field lines thread the system along the axial direction that spans the length L and are line-tied at the top and bottom plates in a motionless photosphere. The magnetic field b initially has only large scales, and is not in equilibrium. We show that the magnetic relaxation leads to the formation of current sheets when the intensity of the magnetic field b is beyond a critical value b_c. For values of b below this threshold (b < b_c), line-tying and field-line tension inhibit the formation of current sheets, while above the threshold (b > b_c) they form quickly on fast ideal timescales. In the ideal case, above the magnetic threshold, we show that current sheets thickness decreases in time until it becomes smaller than the grid resolution, with the analyticity strip width δ decreasing at least exponentially, after which the simulations become under-resolved.

  18. Design and biological activity of {beta}-sheet breaker peptide conjugates

    SciTech Connect

    Rocha, Sandra Cardoso, Isabel; Boerner, Hans; Pereira, Maria Carmo; Saraiva, Maria Joao; Coelho, Manuel

    2009-03-06

    The sequence LPFFD (iA{beta}{sub 5}) prevents amyloid-{beta} peptide (A{beta}) fibrillogenesis and neurotoxicity, hallmarks of Alzheimer's disease (AD), as previously demonstrated. In this study iA{beta}{sub 5} was covalently linked to poly(ethylene glycol) (PEG) and the activity of conjugates was assessed and compared to the activity of the peptide alone by in vitro studies. The conjugates were characterized by MALDI-TOF. Competition binding assays established that conjugates retained the ability to bind A{beta} with similar strength as iA{beta}{sub 5}. Transmission electron microscopy analysis showed that iA{beta}{sub 5} conjugates inhibited amyloid fibril formation, which is in agreement with binding properties observed for the conjugates towards A{beta}. The conjugates were also able to prevent amyloid-induced cell death, as evaluated by activation of caspase 3. These results demonstrated that the biological activity of iA{beta}{sub 5} is not affected by the pegylation process.

  19. CURRENT SHEETS FORMATION IN TANGLED CORONAL MAGNETIC FIELDS

    SciTech Connect

    Rappazzo, A. F.; Parker, E. N. E-mail: parker@oddjob.uchicago.edu

    2013-08-10

    We investigate the dynamical evolution of magnetic fields in closed regions of solar and stellar coronae. To understand under which conditions current sheets form, we examine dissipative and ideal reduced magnetohydrodynamic models in Cartesian geometry, where two magnetic field components are present: the strong guide field B{sub 0}, extended along the axial direction, and the dynamical orthogonal field b. Magnetic field lines thread the system along the axial direction that spans the length L and are line-tied at the top and bottom plates. The magnetic field b initially has only large scales, with its gradient (current) length scale of the order of l{sub b}. We identify the magnetic intensity threshold b/B{sub 0} {approx} l{sub b}/L. For values of b below this threshold, field-line tension inhibits the formation of current sheets, while above the threshold they form quickly on fast ideal timescales. In the ideal case, above the magnetic threshold, we show that current sheets thickness decreases in time until it becomes smaller than the grid resolution, with the analyticity strip width {delta} decreasing at least exponentially, after which the simulations become underresolved.

  20. Study of the {beta}-{alpha} phase transformations of a Ti-64 sheet induced from a high-temperature {beta} state and a high-temperature {alpha} + {beta} state

    SciTech Connect

    Moustahfid, H.; Gey, N.; Humbert, M.; Philippe, M.J.

    1997-01-01

    The room-temperature {alpha} textures of Ti-64 sheets, inherited from the {beta}-{alpha} phase transformation of high-temperature {beta} textures of the material in the {beta} and {alpha} + {beta} fields, respectively, have been studied. The corresponding high-temperature {beta} textures were also determined by a method developed in their laboratory. The knowledge of the high-temperature {beta} textures allows discussions of the variant selections through transformation modeling. As a result, a variant selection occurs in the presence of the stable {alpha} grains of the {alpha} + {beta} field.

  1. Moulin distribution and formation on the southwest Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Chu, V. W.; Smith, L. C.; Gleason, C. J.; Yang, K.; Poinar, K.; Joughin, I.; Pitcher, L. H.

    2015-12-01

    River moulins represent a significant connection between surface meltwater generated on the Greenland ice sheet and subglacial drainage networks, where increased meltwater can enhance ice sliding dynamics. In this study, a new high-resolution moulin map is created from WorldView-1/2 imagery acquired during the 2012 record melt year for a 12,500 km2 area near Russell Glacier in southwest Greenland. A total of 1,236 moulins are mapped and categorized as being located: in crevasse fields, along a single ice fracture, within drained lake basins, or having no visible formation mechanism. We find the presence of moulins up to 1787 m elevation, with 11% of moulins found above 1600 m elevation: higher than previously mapped moulins and where glaciological theory suggests few moulins should form. Our study observes moulins in both extensional and compressional ice flow regimes (28% of moulins are found in areas of high extensional strain rate >0.005 yr-1), suggesting that strain rates are not a strong indicator of the likelihood for moulin formation. Overall, moulin density tends to increase with higher bed elevation, thinner ice, lower surface slope, higher velocity, and higher strain rate. In sum, moulins are most common in crevassed, thinner ice near the ice sheet edge, but significant quantities also develop at high elevations. This indicates that future inland expansion of melting may create hydrologic connections between the surface and the bed at higher elevations than previously thought.

  2. Blue color formation of cyanobacteria with beta-cyclocitral.

    PubMed

    Harada, Ken-Ichi; Ozaki, Keiko; Tsuzuki, Sayaka; Kato, Hajime; Hasegawa, Masateru; Kuroda, Emilia K; Arii, Suzue; Tsuji, Kiyomi

    2009-11-01

    Volatile compounds, such as beta-cyclocitral, geosmin, and 2-methylisoborneol, from cyanobacteria showed a lytic activity against cyanobacteria. Particularly, beta-cyclocitral caused an interesting color change in the culture broth from green to blue during the lysis process. In the present study, the lytic behavior of various cyanobacteria with beta-cyclocitral was investigated, and a mechanism for the blue color formation was developed. beta-Cyclocitral lysed both the laboratory strains of any genera and bloom samples including many species of cyanobacteria, and caused the characteristic color change from green to blue. beta-Cyclocitral provided a characteristic behavior, such that the absorption maxima of chlorophyll-a and beta-carotene disappeared, but that of phycocyanin still remained after 12 h, which indicated that beta-cyclocitral decomposed chlorophyll-a and beta-carotene rapidly, so that the inherent colors from the tolerant water-soluble pigments became observable in the cultured broth. This phenomenon was confirmed by another experiment using Phormidium (NIES-611), which showed a pink color derived from phycoerythrin. beta-Cyclocitral was more easily oxidized when compared with similar aldehyde compounds, so that the pH of the solution quickly decreased to 4.5. An oxidation product of beta-cyclocitral in water solution was isolated and identified as 2,6,6-trimethylcyclohexene-1-carboxylic acid. This study provides support that beta-cyclocitral derived from cyanobacteria plays an important role in the lysis of cyanobacteria and participates in the blue color formation under natural conditions.

  3. An exact collisionless equilibrium for the Force-Free Harris Sheet with low plasma beta

    SciTech Connect

    Allanson, O. Neukirch, T. Wilson, F. Troscheit, S.

    2015-10-15

    We present a first discussion and analysis of the physical properties of a new exact collisionless equilibrium for a one-dimensional nonlinear force-free magnetic field, namely, the force-free Harris sheet. The solution allows any value of the plasma beta, and crucially below unity, which previous nonlinear force-free collisionless equilibria could not. The distribution function involves infinite series of Hermite polynomials in the canonical momenta, of which the important mathematical properties of convergence and non-negativity have recently been proven. Plots of the distribution function are presented for the plasma beta modestly below unity, and we compare the shape of the distribution function in two of the velocity directions to a Maxwellian distribution.

  4. Factors contributing to decreased protein stability when aspartic acid residues are in {beta}-sheet regions.

    SciTech Connect

    Pokkuluri, P. R.; Cai, X.; Raffen, R.; Gu, M.; Stevens, F. J.; Schiffer, M.

    2002-07-01

    Asp residues are significantly under represented in {beta}-sheet regions of proteins, especially in the middle of {beta}-strands, as found by a number of studies using statistical, modeling, or experimental methods. To further understand the reasons for this under representation of Asp, we prepared and analyzed mutants of a {beta}-domain. Two Gln residues of the immunoglobulin light-chain variable domain (V{sub L}) of protein Len were replaced with Asp, and then the effects of these changes on protein stability and protein structure were studied. The replacement of Q38D, located at the end of a {beta}-strand, and that of Q89D, located in the middle of a {beta}-strand, reduced the stability of the parent immunoglobulin VL domain by 2.0 kcal/mol and 5.3 kcal/mol, respectively. Because the Q89D mutant of the wild-type V{sub L}-Len domain was too unstable to be expressed as a soluble protein, we prepared the Q89D mutant in a triple mutant background, V{sub L}-Len M4L/Y27dD/T94H, which was 4.2 kcal/mol more stable than the wild-type V{sub L}-Len domain. The structures of mutants V{sub L}-Len Q38D and V{sub L}-Len Q89D/M4L/Y27dD/T94H were determined by X-ray diffraction at 1.6 A resolution. We found no major perturbances in the structures of these QD mutant proteins relative to structures of the parent proteins. The observed stability changes have to be accounted for by cumulative effects of the following several factors: (1) by changes in main-chain dihedral angles and in side-chain rotomers, (2) by close contacts between some atoms, and, most significantly, (3) by the unfavorable electrostatic interactions between the Asp side chain and the carbonyls of the main chain. We show that the Asn side chain, which is of similar size but neutral, is less destabilizing. The detrimental effect of Asp within a {beta}-sheet of an immunoglobulin-type domain can have very serious consequences. A somatic mutation of a {beta}-strand residue to Asp could prevent the expression of the

  5. Formation and dynamical history of the beta Pictoris system

    NASA Astrophysics Data System (ADS)

    Wyatt, M.

    2014-09-01

    The structure of the beta Pic disk holds many clues to its formation and dynamical history. In particular there is strong evidence for sculpting by the beta Pic-b planet. For example, a warp in the disk at 80au is thought to be driven by the secular perturbations of that planet, and scattering of comets by beta Pic-b is thought to be the origin of the Falling Evaporating Bodies. A clump in the disk coincident with the warp, also at ~80au, provides clues to the outer planetary system which for now is poorly constrained. One possible origin for the clump is in trapping of comets into resonance with an outer planet currently at ~60au, with an alternative scenario being a giant impact between planetary embryos. This talk will consider the various disk structures and what they tell us about the formation and dynamical history of the beta Pictoris system.

  6. Microphase Separation Controlled beta-Sheet Crystallization Kinetics in Fibrous Proteins

    SciTech Connect

    Hu, X.; Lu, Q; Kaplan, D; Cebe, P

    2009-01-01

    Silk is a naturally occurring fibrous protein with a multiblock chain architecture. As such, it has many similarities with synthetic block copolymers, including the possibility for e-sheet crystallization restricted within the crystallizable blocks. The mechanism of isothermal crystallization kinetics of e-sheet crystals in silk multiblock fibrous proteins is reported in this study. Kinetics theories, such as Avrami analysis which was established for studies of synthetic polymer crystal growth, are for the first time extended to investigate protein self-assembly in e-sheet rich Bombyx mori silk fibroin samples, using time-resolved Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and synchrotron real-time wide-angle X-ray scattering (WAXS). The Avrami exponent, n, was close to 2 for all methods and crystallization temperatures, indicating formation of e-sheet crystals in silk proteins is different from the 3-D spherulitic crystal growth found in synthetic polymers. Observations by scanning electron microscopy support the view that the protein structures vary during the different stages of crystal growth, and show a microphase separation pattern after chymotrypsin enzyme biodegradation. We present a model to explain the crystallization of the multiblock silk fibroin protein, by analogy to block copolymers: crystallization of e-sheets occurs under conditions of geometrical restriction caused by phase separation of the crystallizable and uncrystallizable blocks. This crystallization model could be widely applicable in other proteins with multiblock (i.e., crystallizable and noncrystallizable) domains.

  7. Strength limit of entropic elasticity in beta-sheet protein domains.

    PubMed

    Keten, Sinan; Buehler, Markus J

    2008-12-01

    Elasticity and strength of individual beta-sheet protein domains govern key biological functions and the mechanical properties of biopolymers including spider silk, amyloids, and muscle fibers. The worm-like-chain (WLC) model is commonly used to describe the entropic elasticity of polypeptides and other biomolecules. However, force spectroscopy experiments have shown pronounced deviations from the ideal WLC behavior, leading to controversial views about the appropriate elastic description of proteins at nanoscale. Here we report a simple model that explains the physical mechanism that leads to the breakdown of the WLC idealization in experiments by using only two generic parameters of the protein domain, the H-bond energy and the protein backbone's persistence length. We show that a rupture initiation condition characterized by the free energy release rate of H-bonds characterizes the limit of WLC entropic elasticity of beta-sheet protein domains and the onset of rupture. Our findings reveal that strength and elasticity are coupled and cannot be treated separately. The predictions of the model are compared with atomic force microscopy experiments of protein rupture.

  8. Strength limit of entropic elasticity in beta-sheet protein domains

    NASA Astrophysics Data System (ADS)

    Keten, Sinan; Buehler, Markus J.

    2008-12-01

    Elasticity and strength of individual beta-sheet protein domains govern key biological functions and the mechanical properties of biopolymers including spider silk, amyloids, and muscle fibers. The worm-like-chain (WLC) model is commonly used to describe the entropic elasticity of polypeptides and other biomolecules. However, force spectroscopy experiments have shown pronounced deviations from the ideal WLC behavior, leading to controversial views about the appropriate elastic description of proteins at nanoscale. Here we report a simple model that explains the physical mechanism that leads to the breakdown of the WLC idealization in experiments by using only two generic parameters of the protein domain, the H-bond energy and the protein backbone’s persistence length. We show that a rupture initiation condition characterized by the free energy release rate of H-bonds characterizes the limit of WLC entropic elasticity of beta-sheet protein domains and the onset of rupture. Our findings reveal that strength and elasticity are coupled and cannot be treated separately. The predictions of the model are compared with atomic force microscopy experiments of protein rupture.

  9. A beta-sheet interaction interface directs the tetramerisation of the Miz-1 POZ domain.

    PubMed

    Stead, Mark A; Trinh, Chi H; Garnett, James A; Carr, Stephen B; Baron, Andrew J; Edwards, Thomas A; Wright, Stephanie C

    2007-11-02

    The POZ/BTB domain is an evolutionarily conserved motif found in approximately 40 zinc-finger transcription factors (POZ-ZF factors). Several POZ-ZF factors are implicated in human cancer, and POZ domain interaction interfaces represent an attractive target for therapeutic intervention. Miz-1 (Myc-interacting zinc-finger protein) is a POZ-ZF factor that regulates DNA-damage-induced cell cycle arrest and plays an important role in human cancer by virtue of its interaction with the c-Myc and BCL6 oncogene products. The Miz-1 POZ domain mediates both self-association and the recruitment of non-POZ partners. POZ-ZF factors generally function as homodimers, although higher-order associations and heteromeric interactions are known to be physiologically important; crucially, the interaction interfaces in such large complexes have not been characterised. We report here the crystal structure of the Miz-1 POZ domain up to 2.1 A resolution. The tetrameric organisation of Miz-1 POZ reveals two types of interaction interface between subunits; an interface of alpha-helices resembles the dimerisation interface of reported POZ domain structures, whereas a novel beta-sheet interface directs the association of two POZ domain dimers. We show that the beta-sheet interface directs the tetramerisation of the Miz-1 POZ domain in solution and therefore represents a newly described candidate interface for the higher-order homo- and hetero-oligomerisation of POZ-ZF proteins in vivo.

  10. Designing biomaterials exploiting beta-sheet forming peptides self-assembly

    NASA Astrophysics Data System (ADS)

    Saiani, Alberto

    2013-03-01

    The use of non-covalent self-assembly to construct materials has become a prominent strategy in material science offering practical routes for the construction of increasingly functional materials for a variety of applications ranging from electronic to biotechnology. A variety of molecular building blocks can be used for this purpose, one such block that has attracted considerable attention are de-novo designed peptides. The library of 20 natural amino acids offers the ability to play with the intrinsic properties of the peptide such as structure, hydrophobicity, charge and functionality allowing the design of materials with a wide range of properties. The beta-sheet motif is of particular interest as short peptides can be designed to form beta-sheet rich fibres that entangle and consequently form hydrogels. These hydrogels can be further functionalised using specific biological signals or drugs by synthesising functionalised peptides that are incorporated into the hydrogel network during the self-assembling process. This functionalisation approach is very attractive has it does not require any chemistry avoiding therefore the use of additional potentially toxic chemicals. It also offers the possibility to introduce multiple functionalities in a straightforward fashion. The hydrogels can also be made responsive through the use of enzymatic catalysis and/or conjugation with responsive polymers. In this presentation we will discuss the design opportunities offered by these peptides to create new functional biomaterials.

  11. Biomimetic deposition of hydroxyapatite on a synthetic polypeptide with beta sheet structure in a solution mimicking body fluid.

    PubMed

    Takeuchi, Akari; Ohtsuki, Chikara; Kamitakahara, Masanobu; Ogata, Shin-ichi; Miyazaki, Toshiki; Tanihara, Masao

    2008-01-01

    Deposition of a hydroxyapatite layer with similar structure to bone mineral is an attractive approach to the fabrication of bioactive coating layers to achieve direct bonding to living bone. To get successful coating of a hydroxyapatite layer on an organic polymer using a biomimetic solution, it is essential to find organic substrates that can effectively induce heterogeneous nucleation of hydroxyapatite after exposure to the body environment. Our previous study showed that sericin, a type of silk protein, has the ability to induce hydroxyapatite nucleation in a biomimetic solution when the sericin has a beta sheet structure. To confirm the effectiveness of the beta sheet structure in hydroxyapatite nucleation, we focused on investigating hydroxyapatite deposition on a synthetic polypeptide with a beta sheet structure in a biomimetic solution. The beta sheet forming polypeptides with and without carboxyl groups, poly(FE)(3)FG, poly(FQ)(3)FG, poly(LE)(3)LG and poly(LQ)(3)LG, were synthesized in this study. All the polypeptides had mainly beta sheet structure. After soaking the polypeptide films in 1.5SBF, which has 1.5 times the inorganic ion concentrations of human blood plasma, hydroxyapatite formed on the surfaces of the polypeptides with carboxyl groups, poly(FE)(3)FG and poly(LE)(3)LG, within 2 days, but not on those without carboxyl groups, poly(FQ)(3)FG and poly(LQ)(3)LG. We confirmed that the beta sheet structure was effective for hydroxyapatite nucleation even in the synthetic polypeptide. This finding is useful for the future design of organic polymers that can effectively induce nucleation of hydroxyapatite.

  12. Collective behavior in two-dimensional biological systems: Receptor clustering and beta-sheet aggregation

    NASA Astrophysics Data System (ADS)

    Guo, Chinlin

    We studied two particular biomedical systems which exhibit collective molecular behavior. One is clustering of tumor necrosis factor receptor I (TNFR1), and another is β-sheet folding and aggregation. Receptor clustering has been shown to be a crucial step in many signaling events but its biological meaning has not been adequately addressed. Here, via a simple lattice model, we show how cells use this clustering machinery to enhance sensitivity as well as robustness. On the other hand, intracellular deposition of aggregated protein rich in β-sheet is a prominent cytopathological feature of most neurodegenerative diseases. How this aggregation occurs and how it responds to therapy is not completely understood. Here, we started from a reconstruction of the H-bond potential and carry out a full investigation of β-sheet thermodynamics as well as kinetics. We show that β-sheet aggregation is most likely due to molecular stacking and found that the minimal length of an aggregate mutant polymer corresponds well with the number observed in adult Huntington's disease. We have also shown that molecular agents such as dendrimers might fail at high-dose therapy; instead, a potential therapy strategy is to block β-turn formation. Our predictions can be used for future experimental tests and clinical trials.

  13. Reversible hydrogel-solution system of silk with high beta-sheet content.

    PubMed

    Bai, Shumeng; Zhang, Xiuli; Lu, Qiang; Sheng, Weiqin; Liu, Lijie; Dong, Boju; Kaplan, David L; Zhu, Hesun

    2014-08-11

    Silkworm silk has been widely used as a textile fiber, as biomaterials and in optically functional materials due to its extraordinary properties. The β-sheet-rich natural nanofiber units of about 10-50 nm in diameter are often considered the origin of these properties, yet it remains unclear how silk self-assembles into these hierarchical structures. A new system composed of β-sheet-rich silk nanofibers about 10-20 nm in diameter is reported here, where these nanofibers formed into "flowing hydrogels" at 0.5-2% solutions and could be transformed back into the solution state at lower concentrations, even with a high β-sheet content. This is in contrast with other silk processed materials, where significant β-sheet content negates reversibility between solution and solid states. These fibers are formed by regulating the self-assembly process of silk in aqueous solution, which changes the distribution of negative charges while still supporting β-sheet formation in the structures. Mechanistically, there appears to be a shift toward negative charges along the outside of the silk nanofibers in our present study, resulting in a higher zeta potential (above -50 mV) than previous silk materials which tend to be below -30 mV. The higher negative charge on silk nanofibers resulted in electrostatic repulsion strong enough to negate further assembly of the nanofibers. Changing silk concentration changed the balance between hydrophobic interactions and electrostatic repulsion of β-sheet-rich silk nanofibers, resulting in reversible hydrogel-solution transitions. Furthermore, the silk nanofibers could be disassembled into shorter fibers and even nanoparticles upon ultrasonic treatment following the transition from hydrogel to solution due to the increased dispersion of hydrophobic smaller particles, without the loss of β-sheet content, and with retention of the ability to transition between hydrogel and solution states through reversion to longer nanofibers during self

  14. Structure of current and plasma in current sheets depending on the conditions of sheet formation

    NASA Astrophysics Data System (ADS)

    Frank, A. G.; Ostrovskaya, G. V.; Yushkov, E. V.; Artemyev, A. V.; Satunin, S. N.

    2017-01-01

    The structure of current sheets created under laboratory conditions is characterized by a large variety, which depends substantially on the conditions under which the sheet if formed. In this work, we present the results of an experimental study of the structure and evolution of current sheets that were formed in magnetic configurations with a singular line of the X type. It has been shown that the change in the transverse magnetic field gradient, the strength of the longitudinal magnetic field, and the mass of the ions in plasma makes it possible to significantly vary the main parameters of the current sheets. This offers the challenges of using laboratory experimental results for analyzing and simulating the cosmophysical processes.

  15. Differential stability of beta-sheets and alpha-helices in beta-lactamase: a high temperature molecular dynamics study of unfolding intermediates.

    PubMed Central

    Vijayakumar, S; Vishveshwara, S; Ravishanker, G; Beveridge, D L

    1993-01-01

    beta-Lactamase, which catalyzes beta-lactam antibiotics, is prototypical of large alpha/beta proteins with a scaffolding formed by strong noncovalent interactions. Experimentally, the enzyme is well characterized, and intermediates that are slightly less compact and having nearly the same content of secondary structure have been identified in the folding pathway. In the present study, high temperature molecular dynamics simulations have been carried out on the native enzyme in solution. Analysis of these results in terms of root mean square fluctuations in cartesian and [phi, psi] space, backbone dihedral angles and secondary structural hydrogen bonds forms the basis for an investigation of the topology of partially unfolded states of beta-lactamase. A differential stability has been observed for alpha-helices and beta-sheets upon thermal denaturation to putative unfolding intermediates. These observations contribute to an understanding of the folding/unfolding processes of beta-lactamases in particular, and other alpha/beta proteins in general. Images FIGURE 1 FIGURE 4 PMID:8312470

  16. Hybrid modeling of the formation and structure of thin current sheets in the magnetotail

    NASA Technical Reports Server (NTRS)

    Hesse, Michael; Winske, Dan; Birn, Joachim

    1996-01-01

    Hybrid simulations are used to investigate the formation of a thin current sheet inside the plasma sheet of a magnetotail-like configuration. The initial equilibrium is subjected to a driving electric field which is qualitatively similar to what would be expected from solar wind driving. As a result, a new current sheet with the thickness of approximately the ion inertial length is formed. The current density inside the current sheet region is supplied largely by the electrons. Ion acceleration in the cross-tail direction is absent as the driving electric field fails to penetrate into the equatorial region.

  17. Benchmarking the thermodynamic analysis of water molecules around a model beta sheet.

    PubMed

    Huggins, David J

    2012-06-05

    Water molecules play a vital role in biological and engineered systems by controlling intermolecular interactions in the aqueous phase. Inhomogeneous fluid solvation theory provides a method to quantify solvent thermodynamics from molecular dynamics or Monte Carlo simulations and provides an insight into intermolecular interactions. In this study, simulations of TIP4P-2005 and TIP5P-Ewald water molecules around a model beta sheet are used to investigate the orientational correlations and predicted thermodynamic properties of water molecules at a protein surface. This allows the method to be benchmarked and provides information about the effect of a protein on the thermodynamics of nearby water molecules. The results show that the enthalpy converges with relatively little sampling, but the entropy and thus the free energy require considerably more sampling to converge. The two water models yield a very similar pattern of hydration sites, and these hydration sites have very similar thermodynamic properties, despite notable differences in their orientational preferences. The results also predict that a protein surface affects the free energy of water molecules to a distance of approximately 4.0 Å, which is in line with previous work. In addition, all hydration sites have a favorable free energy with respect to bulk water, but only when the water-water entropy term is included. A new technique for calculating this term is presented and its use is expected to be very important in accurately calculating solvent thermodynamics for quantitative application.

  18. The peculiarities of formation of thin current sheet in the Earth's magnetotail

    NASA Astrophysics Data System (ADS)

    Kropotkin, Alexey; Artemyev, Anton; Malova, Helmi; Domrin, Vladimir

    We investigate the process of self-consistent thinning of magnetotail current sheet in the presence of the evolving magnetic field normal component Bz, which usually decreases during the substorm growth phase. Using PIC codes to describe plasma processes with ions becoming demagnetized and electrons being considered as the cold neutralizing background, we show that the appearance of the self-consistent electric field component inside CS can lead to the current sheet thinning and to the appearance of an extremely thin current sheet with thickness close to the ion gyroradius. Due to particle [ExB] drift during the current sheet evolution, the enhanced trapping of ions near the current sheet central plane takes place. It is shown that the density of quasi-trapped particles around current sheet at the final stage depends on both the value of the initial magnetic field normal component Bz, and the speed of the Bz decrease. If the initial magnetic field normal component is less than about 0.14 of the tangential field at the edges, the trapped plasma density near the current sheet is small. As a result, the above mentioned extremely thin current sheet is formed. In the opposite case, when the initial normal component related to the tangential field is larger than 0.14, the density of trapped particles is much higher, which produces effective thickening of the current sheet. In both cases transient (Speiser) ions are the main current carriers, but in the second case local diamagnetic currents of the trapped plasma perturb the сurrent sheet profile making it thicker. Also trapped particles can be responsible for intense negative currents at the current sheet edges. During the Bz decrease, an additional effect of ion polarization drifts in the Y direction can compete with these negative diamagnetic fields of quasi-trapped ions. Therefore the ion dynamics is probably the general mechanism which contributes to the formation of thin current sheet and its fine structure.

  19. Current Sheet Formation in a Conical Theta Pinch Faraday Accelerator with Radio-frequency Assisted Discharge

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Hallock, Ashley K.; Choueiri, Edgar Y.

    2008-01-01

    Data from an inductive conical theta pinch accelerator are presented to gain insight into the process of inductive current sheet formation in the presence of a preionized background gas produced by a steady-state RF-discharge. The presence of a preionized plasma has been previously shown to allow for current sheet formation at lower discharge voltages and energies than those found in other pulsed inductive accelerator concepts, leading to greater accelerator efficiencies at lower power levels. Time-resolved magnetic probe measurements are obtained for different background pressures and pulse energies to characterize the effects of these parameters on current sheet formation. Indices are defined that describe time-resolved current sheet characteristics, such as the total current owing in the current sheet, the time-integrated total current ('strength'), and current sheet velocity. It is found that for a given electric field strength, maximums in total current, strength, and velocity occur for one particular background pressure. At other pressures, these current sheet indices are considerably smaller. The trends observed in these indices are explained in terms of the principles behind Townsend breakdown that lead to a dependence on the ratio of the electric field to the background pressure. Time-integrated photographic data are also obtained at the same experimental conditions, and qualitatively they compare quite favorably with the time-resolved magnetic field data.

  20. Membrane Pore Formation by Amyloid beta (25-35) Peptide

    NASA Astrophysics Data System (ADS)

    Kandel, Nabin; Tatulian, Suren

    Amyloid (A β) peptide contributes to Alzheimer's disease by a yet unidentified mechanism. One of the possible mechanisms of A β toxicity is formation of pores in cellular membranes. We have characterized the formation of pores in phospholipid membranes by the Aβ25 - 35 peptide (GSNKGAIIGLM) using fluorescence, Fourier transform infrared spectroscopy (FTIR) and circular dichroism (CD) techniques. CD and FTIR identified formation of β-sheet structure upon incubation of the peptide in aqueous buffer for 2 hours. Unilamellar vesicles composed of a zwitterionic lipid, 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC), and 70 % POPC plus 30 % of an acidic lipid, 1-palmitoyl-2-oleoyl-phosphatidylglycerol (POPG), are made in 30 mM CaCl2. Quin-2, a fluorophore that displays increased fluorescence upon Ca2+ binding, is added to the vesicles externally. Peptide addition results in increased Quin-2 fluorescence, which is interpreted by binding of the peptide to the vesicles, pore formation, and Ca2+ leakage. The positive and negative control measurements involve addition of a detergent, Triton X-100, which causes vesicle rupture and release of total calcium, and blank buffer, respectively.

  1. Spontaneous formation of electric current sheets and the origin of solar flares

    NASA Technical Reports Server (NTRS)

    Low, B. C.; Wolfson, R.

    1988-01-01

    It is demonstrated that the continuous boundary motion of a sheared magnetic field in a tenuous plasma with an infinite electrical conductivity can induce the formation of multiple electric current sheets in the interior plasma. In response to specific footpoint displacements, the quadrupolar magnetic field considered is shown to require the formation of multiple electric current sheets as it achieves a force-free state. Some of the current sheets are found to be of finite length, running along separatrix lines of force which separate lobes of magnetic flux. It is suggested that current sheets in the form of infinitely thin magnetic shear layers may be unstable to resistive tearing, a process which may have application to solar flares.

  2. Development of the dual scintillator sheet and Phoswich detector for simultaneous Alpha- and Beta-rays measurement

    SciTech Connect

    Seo, B.K.; Kim, G.H.; Park, C.H.; Jung, Y.H.; Jung, C.H.; Lee, K.W.; Han, M.J.

    2007-07-01

    Thin sheet type of ZnS(Ag)/plastic dual scintillator for simultaneous counting of alpha- and beta-particles using a organic and inorganic scintillator widely used in the radiation measurement was manufactured, which could be applicable in the contamination monitoring systems. Counting materials were manufactured by solidification of the scintillator solution which mixed scintillator, solvent, and polymer. Prepared dual scintillator is a counting material which can simultaneously measure the alpha- and beta-particles. It was divided into two parts : an inorganic scintillator layer for alpha-particle detection and an organic one for beta-particle detection. The organic layer was composed of 2,5-diphenyloxazole [PPO] and 1,4,-bis[5-phenyl(oxazolyl)benzene] [POPOP] acting as the scintillator and polysulfone acting as the polymer. The inorganic layer was composed of ZnS(Ag) as scintillator and polysulfone as paste. The ZnS(Ag) scintillator layer was printed onto the organic layer using screen printing method. To estimate the detection ability of the prepared counting materials, alpha-particle emitting nuclide, Am-241, and beta emitting nuclide, Sr/Y-90, were used. The scintillations produced by interaction between radiation and scintillator were measured by photomultiplier tube. The overall counting results reveal that the developed detector is efficient for simultaneous counting of alpha- and beta-particles. For application test, the dual scintillator was fabricated with a Phoswich detector for monitoring the in-pipe alpha and beta contamination. To deploy inside a pipe, two types of Phoswich detectors, sheets and cylinders, were prepared. For in-pipe monitoring, it was found that the cylindrical type was excellent. In the study, polymer composite counting material and Phoswich detectors were prepared using organic and inorganic scintillator for detecting different radiations. In the future, it will be applied to the contamination monitoring system for nuclear

  3. Venus' Atla and Beta Regiones: Formation of Chasmata and Coronae

    NASA Astrophysics Data System (ADS)

    Stoddard, P. R.; Jurdy, D. M.

    2004-12-01

    Two likely areas of current tectonic and volcanic activity on Venus are Atla and Beta Regiones. Both are marked by pronounced topographic and geoid highs and each lies at the intersection of multiple rifts, i.e. the chasmata system. These regiones may be surface expressions of mantle upwellings. We examine the distribution, style, and attitude of coronae with respect to the two geoid highs. Coronae -- circular features unique to Venus -- could be caused by individual rising diapirs. Unlike Earth, Venus shows little evidence of horizontal motion, resulting in juxtaposition of coronae of all ages. Furthermore, there is little erosion to modify features. In our analysis, we use the three-tiered classification (based on the interior morphology) of 394 coronae, hence termed domal, circular, and calderic. These differing styles may reflect different stages in the evolution of a corona: from domal (youngest, possibly still active) features, progressing through increasing degrees of collapse to the calderic coronae. Comparing locations of these features shows the domal coronae average higher elevations, and calderic at lower elevations, with circular in between. Similar comparisons of other characteristics of the coronae, such as size, elongation, or dip, also show the progression from domal through calderic to circular. Both Atla and Beta are ringed by many coronae, but neither has coronae at or near their crests even within 20 m of their geoid highs. Coronae do occur in many rift segments, yet none occurs at or near these intersection points. Perhaps just as remarkable, Atla has a partial ring of four domal coronae, all within a 10-m geoid range of each other, whereas Beta has a partial ring of 6 or so calderic coronae between three and four 10-m contours from its crest. In both instances, the rings parallel geoid contour lines. These are the nearest coronae of their type to the crests. If corona formation is contemporaneous with the uplift process at Atla and Beta, and

  4. Effects of side-chain orientation on the 13C chemical shifts of antiparallel beta-sheet model peptides.

    PubMed

    Villegas, Myriam E; Vila, Jorge A; Scheraga, Harold A

    2007-02-01

    The dependence of the (13)C chemical shift on side-chain orientation was investigated at the density functional level for a two-strand antiparallel beta-sheet model peptide represented by the amino acid sequence Ac-(Ala)(3)-X-(Ala)(12)-NH(2) where X represents any of the 17 naturally occurring amino acids, i.e., not including alanine, glycine and proline. The dihedral angles adopted for the backbone were taken from, and fixed at, observed experimental values of an antiparallel beta-sheet. We carried out a cluster analysis of the ensembles of conformations generated by considering the side-chain dihedral angles for each residue X as variables, and use them to compute the (13)C chemical shifts at the density functional theory level. It is shown that the adoption of the locally-dense basis set approach for the quantum chemical calculations enabled us to reduce the length of the chemical-shift calculations while maintaining good accuracy of the results. For the 17 naturally occurring amino acids in an antiparallel beta-sheet, there is (i) good agreement between computed and observed (13)C(alpha) and (13)C(beta) chemical shifts, with correlation coefficients of 0.95 and 0.99, respectively; (ii) significant variability of the computed (13)C(alpha) and (13)C(beta) chemical shifts as a function of chi(1) for all amino acid residues except Ser; and (iii) a smaller, although significant, dependence of the computed (13)C(alpha) chemical shifts on chi(xi) (with xi > or = 2) compared to chi(1) for eleven out of seventeen residues. Our results suggest that predicted (13)C(alpha) and (13)C(beta) chemical shifts, based only on backbone (phi,psi) dihedral angles from high-resolution X-ray structure data or from NMR-derived models, may differ significantly from those observed in solution if the dihedral-angle preferences for the side chains are not taken into account.

  5. Dynamo-driven plasmoid formation from a current-sheet instability

    NASA Astrophysics Data System (ADS)

    Ebrahimi, F.

    2016-12-01

    Axisymmetric current-carrying plasmoids are formed in the presence of nonaxisymmetric fluctuations during nonlinear three-dimensional resistive MHD simulations in a global toroidal geometry. We utilize the helicity injection technique to form an initial poloidal flux in the presence of a toroidal guide field. As helicity is injected, two types of current sheets are formed from (1) the oppositely directed field lines in the injector region (primary reconnecting current sheet), and (2) the poloidal flux compression near the plasma edge (edge current sheet). We first find that nonaxisymmetric fluctuations arising from the current-sheet instability isolated near the plasma edge have tearing parity but can nevertheless grow fast (on the poloidal Alfven time scale). These modes saturate by breaking up the current sheet. Second, for the first time, a dynamo poloidal flux amplification is observed at the reconnection site (in the region of the oppositely directed magnetic field). This fluctuation-induced flux amplification increases the local Lundquist number, which then triggers a plasmoid instability and breaks the primary current sheet at the reconnection site. The plasmoids formation driven by large-scale flux amplification, i.e., a large-scale dynamo, observed here has strong implications for astrophysical reconnection as well as fast reconnection events in laboratory plasmas.

  6. Dynamo-driven plasmoid formation from a current-sheet instability

    DOE PAGES

    Ebrahimi, F.

    2016-12-15

    Axisymmetric current-carrying plasmoids are formed in the presence of nonaxisymmetric fluctuations during nonlinear three-dimensional resistive MHD simulations in a global toroidal geometry. In this study, we utilize the helicity injection technique to form an initial poloidal flux in the presence of a toroidal guide field. As helicity is injected, two types of current sheets are formed from the oppositely directed field lines in the injector region (primary reconnecting current sheet), and the poloidal flux compression near the plasma edge (edge current sheet). We first find that nonaxisymmetric fluctuations arising from the current-sheet instability isolated near the plasma edge have tearingmore » parity but can nevertheless grow fast (on the poloidal Alfven time scale). These modes saturate by breaking up the current sheet. Second, for the first time, a dynamo poloidal flux amplification is observed at the reconnection site (in the region of the oppositely directed magnetic field). This fluctuation-induced flux amplification increases the local Lundquist number, which then triggers a plasmoid instability and breaks the primary current sheet at the reconnection site. Finally, the plasmoids formation driven by large-scale flux amplification, i.e., a large-scale dynamo, observed here has strong implications for astrophysical reconnection as well as fast reconnection events in laboratory plasmas.« less

  7. Dynamo-driven plasmoid formation from a current-sheet instability

    SciTech Connect

    Ebrahimi, F.

    2016-12-15

    Axisymmetric current-carrying plasmoids are formed in the presence of nonaxisymmetric fluctuations during nonlinear three-dimensional resistive MHD simulations in a global toroidal geometry. In this study, we utilize the helicity injection technique to form an initial poloidal flux in the presence of a toroidal guide field. As helicity is injected, two types of current sheets are formed from the oppositely directed field lines in the injector region (primary reconnecting current sheet), and the poloidal flux compression near the plasma edge (edge current sheet). We first find that nonaxisymmetric fluctuations arising from the current-sheet instability isolated near the plasma edge have tearing parity but can nevertheless grow fast (on the poloidal Alfven time scale). These modes saturate by breaking up the current sheet. Second, for the first time, a dynamo poloidal flux amplification is observed at the reconnection site (in the region of the oppositely directed magnetic field). This fluctuation-induced flux amplification increases the local Lundquist number, which then triggers a plasmoid instability and breaks the primary current sheet at the reconnection site. Finally, the plasmoids formation driven by large-scale flux amplification, i.e., a large-scale dynamo, observed here has strong implications for astrophysical reconnection as well as fast reconnection events in laboratory plasmas.

  8. Cloning of beta-primeverosidase from tea leaves, a key enzyme in tea aroma formation.

    PubMed

    Mizutani, Masaharu; Nakanishi, Hidemitsu; Ema, Jun-ichi; Ma, Seung-Jin; Noguchi, Etsuko; Inohara-Ochiai, Misa; Fukuchi-Mizutani, Masako; Nakao, Masahiro; Sakata, Kanzo

    2002-12-01

    A beta-primeverosidase from tea (Camellia sinensis) plants is a unique disaccharide-specific glycosidase, which hydrolyzes aroma precursors of beta-primeverosides (6-O-beta-D-xylopyranosyl-beta-D-glucopyranosides) to liberate various aroma compounds, and the enzyme is deeply concerned with the floral aroma formation in oolong tea and black tea during the manufacturing process. The beta-primeverosidase was purified from fresh leaves of a cultivar for green tea (C. sinensis var sinensis cv Yabukita), and its partial amino acid sequences were determined. The beta-primeverosidase cDNA has been isolated from a cDNA library of cv Yabukita using degenerate oligonucleotide primers. The cDNA insert encodes a polypeptide consisting of an N-terminal signal peptide of 28 amino acid residues and a 479-amino acid mature protein. The beta-primeverosidase protein sequence was 50% to 60% identical to beta-glucosidases from various plants and was classified in a family 1 glycosyl hydrolase. The mature form of the beta-primeverosidase expressed in Escherichia coli was able to hydrolyze beta-primeverosides to liberate a primeverose unit and aglycons, but did not act on 2-phenylethyl beta-D-glucopyranoside. These results indicate that the beta-primeverosidase selectively recognizes the beta-primeverosides as substrates and specifically hydrolyzes the beta-glycosidic bond between the disaccharide and the aglycons. The stereochemistry for enzymatic hydrolysis of 2-phenylethyl beta-primeveroside by the beta-primeverosidase was followed by (1)H-nuclear magnetic resonance spectroscopy, revealing that the enzyme hydrolyzes the beta-primeveroside by a retaining mechanism. The roles of the beta-primeverosidase in the defense mechanism in tea plants and the floral aroma formation during tea manufacturing process are also discussed.

  9. Formation and stability of the self-consistent one-dimensional tail current sheet

    NASA Technical Reports Server (NTRS)

    Pritchett, P. L.; Coroniti, F. V.

    1992-01-01

    The paper investigates the formation, the structure, and the stability of self-consistent one-dimensional current sheets in which the ions carry most of the current and momentum (the occurrence of which was suggested by observations of Mitchell et al., 1990; and Sergeev et al., 1990). Results of the analysis showed that, for the case of a cold current sheet, the characteristic thickness lamba equals to about (Bz/B0) exp 4/3 c/omega(p0), where Bz is the normal field component, B0 is the asymptotic magnitude of the reversing field, and c/omega(p0)is the collisionless ion skin depth based on lobe density. A two-dimensional self-consistent dynamical simulation model is developed, which demonstrates that these idealized current sheets are unstable to kink perturbations driven by the anisotropic pressure distribution produced by the chaotic nature of the particle orbits in a field-reversal region.

  10. EGCG Inhibited Lipofuscin Formation Based on Intercepting Amyloidogenic β-Sheet-Rich Structure Conversion

    PubMed Central

    Cai, Shuxian; Yang, Heng; Zeng, Kewu; Zhang, Jing; Zhong, Ni; Wang, Yingzi; Ye, Jing; Tu, Pengfei; Liu, Zhonghua

    2016-01-01

    Background Lipofuscin (LF) is formed during lipid peroxidation and sugar glycosylation by carbonyl-amino crosslinks with biomacrolecules, and accumulates slowly within postmitotic cells. The environmental pollution, modern dietary culture and lifestyle changes have been found to be the major sources of reactive carbonyl compounds in vivo. Irreversible carbonyl-amino crosslinks induced by carbonyl stress are essentially toxiferous for aging-related functional losses in modern society. Results show that (-)-epigallocatechin gallate (EGCG), the main polyphenol in green tea, can neutralize the carbonyl-amino cross-linking reaction and inhibit LF formation, but the underlying mechanism is unknown. Methods and Results We explored the mechanism of the neutralization process from protein, cell, and animal levels using spectrofluorometry, infrared spectroscopy, conformation antibodies, and electron microscopy. LF demonstrated an amyloidogenic β-sheet-rich with antiparallel structure, which accelerated the carbonyl-amino crosslinks formation and disrupted proteolysis in both PC12 cells and D-galactose (D-gal)-induced brain aging mice models. Additionally, EGCG effectively inhibited the formation of the amyloidogenic β-sheet-rich structure of LF, and prevented its conversion into toxic and on-pathway aggregation intermediates, thereby cutting off the carbonyl-amino crosslinks. Conclusions Our study indicated that the amyloidogenic β-sheet structure of LF may be the core driving force for carbonyl-amino crosslinks further formation, which mediates the formation of amyloid fibrils from native state of biomacrolecules. That EGCG exhibits anti-amyloidogenic β-sheet-rich structure properties to prevent the LF formation represents a novel strategy to impede the development of degenerative processes caused by ageing or stress-induced premature senescence in modern environments. PMID:27030967

  11. Coronal current-sheet formation - The effect of asymmetric and symmetric shears

    NASA Technical Reports Server (NTRS)

    Karpen, Judith T.; Antiochos, Spiro K.; Devore, C. R.

    1991-01-01

    A 2.5D numerical code is used to investigate the results of an asymmetric shear imposed on a potential quadrupolar magnetic field under two sets of atmospheric boundary conditions - a low-beta plasma with line tying at the base, similar to the line-tied analytic model, and a hydrostatic-equilibrium atmosphere with solar gravity, typical of the observed photosphere-chromosphere interface. The low-beta simulation confirms the crucial role of the line-tying assumption in producting current sheets. The effects of a symmetric shear on the same hydrostatic-equilibrium atmosphere is examined, using more grid points to improve the resolution of the current structures which form along the flux surfaces. It is found that true current sheets do not form in the corona when a more realistic model is considered. The amount of Ohmic dissipation in the thick currents is estimated to be two to four orders of magnitude below that required to heat the corona. It is concluded that magnetic topologies of the type examined here do not contribute significantly to coronal heating.

  12. Formation and Reconnection of Three-Dimensional Current Sheets in the Solar Corona

    NASA Technical Reports Server (NTRS)

    Edmondson, J. K.; Antiochos, S. K.; DeVore, C. R.; Zurbuchen, T. H.

    2010-01-01

    Current-sheet formation and magnetic reconnection are believed to be the basic physical processes responsible for much of the activity observed in astrophysical plasmas, such as the Sun s corona. We investigate these processes for a magnetic configuration consisting of a uniform background field and an embedded line dipole, a topology that is expected to be ubiquitous in the corona. This magnetic system is driven by a uniform horizontal flow applied at the line-tied photosphere. Although both the initial field and the driver are translationally symmetric, the resulting evolution is calculated using a fully three-dimensional magnetohydrodynamic (3D MHD) simulation with adaptive mesh refinement that resolves the current sheet and reconnection dynamics in detail. The advantage of our approach is that it allows us to apply directly the vast body of knowledge gained from the many studies of 2D reconnection to the fully 3D case. We find that a current sheet forms in close analogy to the classic Syrovatskii 2D mechanism, but the resulting evolution is different than expected. The current sheet is globally stable, showing no evidence for a disruption or a secondary instability even for aspect ratios as high as 80:1. The global evolution generally follows the standard Sweet- Parker 2D reconnection model except for an accelerated reconnection rate at a very thin current sheet, due to the tearing instability and the formation of magnetic islands. An interesting conclusion is that despite the formation of fully 3D structures at small scales, the system remains close to 2D at global scales. We discuss the implications of our results for observations of the solar corona. Subject Headings: Sun: corona Sun: magnetic fields Sun: reconnection

  13. Insights into the spontaneous formation of silicene sheet on diboride thin films

    NASA Astrophysics Data System (ADS)

    Fleurence, A.; Yamada-Takamura, Y.

    2017-01-01

    The realization of silicene-free ZrB2(0001) thin films grown on Si(111) by Ar+ ion bombardment allowed for studying the spontaneous formation of silicene on their surfaces. Imaging the bare ZrB2(0001) surface by STM revealed the structures of Zr-terminated and B-terminated ZrB2(0001) created by the bombardment. The spontaneous formation of a continuous silicene sheet on a sputtering-induced disordered ZrB2 surface demonstrates that silicene does not require an atomically-flat crystalline template to be stabilized. This opens the way to the fabrication of large scale single-crystal sheets and points out the potential of silicene to be used in the next generation silicon-based technologies.

  14. Structural characteristics of the beta-sheet-like human and rat islet amyloid polypeptides as determined by scanning tunneling microscopy.

    PubMed

    Mao, Xiaobo; Ma, Xiaojing; Liu, Lei; Niu, Lin; Yang, Yanlian; Wang, Chen

    2009-09-01

    We demonstrate in this work that scanning tunneling microscopy (STM) provides a useful approach to obtaining structural information about human islet amyloid polypeptide (hIAPP) and rat islet amyloid polypeptide (rIAPP) assembly on highly oriented pyrolytic graphite (HOPG) with sub-molecular resolution. The observed hIAPP and rIAPP lamellae consisted of parallel stripes. The STM images of hIAPPs show multiple molecular folding structures, with an average of 11 amino acid residues for the core regions. In addition, the STM images also reveal the assembly characteristics of rIAPP lamellae and may indicate a secondary structural conformation from random coil to beta-sheet-like on the graphite surface.

  15. Dynamically stable beta-sheets in Cu-initiated misfolding of α-synuclein

    NASA Astrophysics Data System (ADS)

    Rose, Francis; Hodak, Miroslav; Bernholc, Jerry

    2008-03-01

    The human protein α-synuclein has been implicated as a central constituent in multiple neurodegenerative diseases. In Parkinson disease it is even thought to be the causative link. α-synuclein can be stimulated to aggregate into deleterious fibrillar structures by mutation, metal binding, and agitation. In particular, Cu^2+ has been found in high concentrations in neural tissues of Parkinson sufferers. We propose a scenario involving the metal ion Cu^2+ as the misfolding β-sheet initiator of fibrillogenesis. A model fragment of the metal-bound protein was investigated using DFT to obtain conformational details of the energetically favorable geometries. Feasible β-sheet structures incorporating the DFT geometries were explored using heuristic β-sheet guidelines and inverse kinematics. The resulting structures were tested for dynamic stability by simulating the fully solvated protein by classical MD constrained by the DFT geometries. Our results indicate that dynamically stable structures exist and that the metal binding is directly responsible for initiating misfolding.

  16. Swelling and folding as mechanisms of 3D shape formation in thin elastic sheets

    NASA Astrophysics Data System (ADS)

    Dias, Marcelo A.

    We work with two different mechanisms to generate geometric frustration on thin elastic sheets; isotropic differential growth and folding. We describe how controlled growth and prescribing folding patterns are useful tools for designing three-dimensional objects from information printed in two dimensions. The first mechanism is inspired by the possibility to control shapes by swelling polymer films, where we propose a solution for the problem of shape formation by asking the question, “what 2D metric should be prescribed to achieve a given 3D shape?”', namely the reverse problem. We choose two different types of initial configurations of sheets, disk-like with one boundary and annular with two boundaries. We demonstrate our technique by choosing four examples of 3D axisymmetric shapes and finding the respective swelling factors to achieve the desired shape. Second, we present a mechanical model for a single curved fold that explains both the buckled shape of a closed fold and its mechanical stiffness. The buckling arises from the geometrical frustration between the prescribed crease angle and the bending energy of the sheet away from the crease. This frustration increases as the sheet's area increases. Stiff folds result in creases with constant space curvature while softer folds inherit the broken symmetry of the buckled shape. We extend the application of our numerical model to show the potential to study multiple fold structures.

  17. Current sheet Formation in a Conical Theta Pinch Faraday Accelerator with Radio-Frequency Assisted Discharge

    NASA Technical Reports Server (NTRS)

    Hallock, Ashley K.; Choueiri, Edgar Y.; Polzin, Kurt A.

    2007-01-01

    The inductive formation of current sheets in a conical theta pinch FARAD (Faraday Accelerator with Radio-frequency Assisted Discharge) thruster is investigated experimentally with time-integrated photography. The goal is to help in understanding the mechanisms and conditions controlling the strength and extent of the current sheet, which are two indices important for FARAD as a propulsion concept. The profiles of these two indices along the inside walls of the conical acceleration coil are assumed to be related to the profiles of the strength and extent of the luminosity pattern derived from photographs of the discharge. The variations of these profiles as a function of uniform back-fill neutral pressure (with no background magnetic field and all parameters held constant) provided the first clues on the nature and qualitative dependencies of current sheet formation. It was found that there is an optimal pressure for which both indices reach a maximum and that the rate of change in these indices with pressure differs on either side of this optimal pressure. This allowed the inference that current sheet formation follows a Townsend-like breakdown mechanism modified by the existence of a finite pressure-dependent radio-frequency-generated electron density background. The observation that the effective location of the luminosity pattern favors the exit-half of the conical coil is explained as the result of the tendency of the inductive discharge circuit to operate near its minimal self-inductance. Movement of the peak in the luminosity pattern towards the upstream side of the cone with increasing pressure is believed to result from the need of the circuit to compensate for the increase in background plasma resistivity due to increasing pressure.

  18. Landscape formation by past continental ice sheets: insights into the subglacial environment

    NASA Astrophysics Data System (ADS)

    Piotrowski, Jan A.

    2014-05-01

    Glaciers and ice sheets are known as most powerful, climatically driven agents of large-scale sediment redistribution and landscape formation in the Earth system. During the Quaternary, repeated waxing and waning of continental ice sheets contributed to profound reshaping of the Earth surface and set the scene for the development of ecosystems in the post-glacial time. Despite the well-established impact of glaciers on the upper lithosphere the specific processes of glacial erosion, transport and deposition and the formation landforms at the ice-bed interface are contentious. In particular, the relative importance of direct ice impact versus the impact of glacial meltwater is highly controversial. Here, we focus on the southern peripheral area of the Scandinavian Ice Sheet hosting thick successions of soft, deformable sediments and examine some spectacular sediment/landform assemblages found nowadays in both terrestrial and marine settings to illustrate the nature of the subglacial processes. In order to decipher the past ice sheet behavior field, experimental and numerical approaches are combined. It is shown that the strength of the coupling between the ice and the bed that controls the response of the substratum to ice overriding and stress propagation depends primarily on the ability of the glacial system to evacuate meltwater from ice-bed interface. Strong coupling, locally enhanced by subglacial permafrost resulted in deeply rooted (100's of meters) glaciotectonic deformation reflected on the surface as ice-shoved hills whereas weak coupling promoted by water accumulating under the ice triggered the formation of deep (100's of meters) tunnel valley networks. Under the arteries of fast-flowing ice known as palaeo-ice streams, remoulding of soft sediments generated mega-scale glacial lineations and drumlins that hold the key to understanding glacier dynamics. The subglacial environment is envisaged as a four-dimensional mosaic of stable and deforming spots

  19. World Sheet Commuting beta-gamma CFT and Non-Relativistic StringTheories

    SciTech Connect

    Kim, Bom Soo

    2007-08-30

    We construct a sigma model in two dimensions with Galilean symmetry in flat target space similar to the sigma model of the critical string theory with Lorentz symmetry in 10 flat spacetime dimensions. This is motivated by the works of Gomis and Ooguri[1] and Danielsson et. al.[2, 3]. Our theory is much simpler than their theory and does not assume a compact coordinate. This non-relativistic string theory has a bosonic matter {beta}{gamma} CFT with the conformal weight of {beta} as 1. It is natural to identify time as a linear combination of {gamma} and {bar {gamma}} through an explicit realization of the Galilean boost symmetry. The angle between {gamma} and {bar {gamma}} parametrizes one parameter family of selection sectors. These selection sectors are responsible for having a non-relativistic dispersion relation without a nontrivial topology in the non-relativistic setup, which is one of the major differences from the previous works[1, 2, 3]. This simple theory is the non-relativistic analogue of the critical string theory, and there are many different avenues ahead to be investigated. We mention a possible consistent generalization of this theory with different conformal weights for the {beta}{gamma} CFT. We also mention supersymmetric generalizations of these theories.

  20. World sheet commuting {beta}{gamma} conformal field theory and nonrelativistic string theories

    SciTech Connect

    Kim, Bom Soo

    2007-11-15

    We construct a sigma model in two dimensions with Galilean symmetry in flat target space similar to the sigma model of the critical string theory with Lorentz symmetry in 10 flat spacetime dimensions. This is motivated by the works of Gomis and Ooguri [J. Math. Phys. (N.Y.) 42, 3127 (2001)] and Danielsson et al. [J. High Energy Phys. 10 (2000) 020; J. High Energy Phys. 03 (2001) 041.]. Our theory is much simpler than their theory and does not assume a compact coordinate. This nonrelativistic string theory has a bosonic matter {beta}{gamma} conformal field theory with the conformal weight of {beta} as 1. It is natural to identify time as a linear combination of {gamma} and {gamma} through an explicit realization of the Galilean boost symmetry. The angle between {gamma} and {gamma} parametrizes one parameter family of selection sectors. These selection sectors are responsible for having a nonrelativistic dispersion relation without a nontrivial topology in the nonrelativistic setup, which is one of the major differences from the previous works of Gomis and Ooguri and of Danielsson and co-workers. This simple theory is the nonrelativistic analogue of the critical string theory, and there are many different avenues ahead to be investigated. We mention a possible consistent generalization of this theory with different conformal weights for the {beta}{gamma} conformal field theory. We also mention supersymmetric generalizations of these theories.

  1. Association thermodynamics and conformational stability of beta-sheet amyloid beta(17-42) oligomers: effects of E22Q (Dutch) mutation and charge neutralization.

    PubMed

    Blinov, Nikolay; Dorosh, Lyudmyla; Wishart, David; Kovalenko, Andriy

    2010-01-20

    Amyloid fibrils are associated with many neurodegenerative diseases. It was found that amyloidogenic oligomers, not mature fibrils, are neurotoxic agents related to these diseases. Molecular mechanisms of infectivity, pathways of aggregation, and molecular structure of these oligomers remain elusive. Here, we use all-atom molecular dynamics, molecular mechanics combined with solvation analysis by statistical-mechanical, three-dimensional molecular theory of solvation (also known as 3D-RISM-KH) in a new MM-3D-RISM-KH method to study conformational stability, and association thermodynamics of small wild-type Abeta(17-42) oligomers with different protonation states of Glu(22), as well the E22Q (Dutch) mutants. The association free energy of small beta-sheet oligomers shows near-linear trend with the dimers being thermodynamically more stable relative to the larger constructs. The linear (within statistical uncertainty) dependence of the association free energy on complex size is a consequence of the unilateral stacking of monomers in the beta-sheet oligomers. The charge reduction of the wild-type Abeta(17-42) oligomers upon protonation of the solvent-exposed Glu(22) at acidic conditions results in lowering the association free energy compared to the wild-type oligomers at neutral pH and the E22Q mutants. The neutralization of the peptides because of the E22Q mutation only marginally affects the association free energy, with the reduction of the direct electrostatic interactions mostly compensated by the unfavorable electrostatic solvation effects. For the wild-type oligomers at acidic conditions such compensation is not complete, and the electrostatic interactions, along with the gas-phase nonpolar energetic and the overall entropic effects, contribute to the lowering of the association free energy. The differences in the association thermodynamics between the wild-type Abeta(17-42) oligomers at neutral pH and the Dutch mutants, on the one hand, and the Abeta(17

  2. In Search of the Attributes Responsible for Sliver Formation in Cold Rolled Steel Sheets

    NASA Astrophysics Data System (ADS)

    Mohanty, Itishree; Das, Prasun; Bhattacharjee, Debashish; Datta, Shubhabrata

    2016-06-01

    Surface quality is one of the most important characteristics of cold rolled (CR) steel sheets for its application in consumer goods industries. The actual cause of sliver formation is very difficult to determine, as it is revealed only after the final cold rolling of the steel. A thorough investigation on searching the root cause of sliver formation in CR steel is done here using several statistical tools towards mining the industrial data for extraction of knowledge. As the complex interactions between the variables make it difficult to identify the cause, it is seen that findings from different techniques differed to a certain extent. Still it is revealed that 21 variables could be short listed as major contributor for sliver formation, but those are found to be from all the areas of the processing. This leads to the conclusion that no particular process variable or particular processing could be held responsible for sliver formation.

  3. In Search of the Attributes Responsible for Sliver Formation in Cold Rolled Steel Sheets

    NASA Astrophysics Data System (ADS)

    Mohanty, Itishree; Das, Prasun; Bhattacharjee, Debashish; Datta, Shubhabrata

    2017-04-01

    Surface quality is one of the most important characteristics of cold rolled (CR) steel sheets for its application in consumer goods industries. The actual cause of sliver formation is very difficult to determine, as it is revealed only after the final cold rolling of the steel. A thorough investigation on searching the root cause of sliver formation in CR steel is done here using several statistical tools towards mining the industrial data for extraction of knowledge. As the complex interactions between the variables make it difficult to identify the cause, it is seen that findings from different techniques differed to a certain extent. Still it is revealed that 21 variables could be short listed as major contributor for sliver formation, but those are found to be from all the areas of the processing. This leads to the conclusion that no particular process variable or particular processing could be held responsible for sliver formation.

  4. Conditions for the formation of nongyrotropic current sheets in slowly evolving plasmas

    SciTech Connect

    Schindler, Karl; Hesse, Michael

    2010-08-15

    This paper addresses the formation of nongyrotropic current sheets resulting from slow external driving. The medium is a collisionless plasma with one spatial dimension and a three-dimensional velocity space. The study is based on particle simulation and an analytical approach. Earlier results that apply to compression of an initial Harris sheet are generalized in several ways. In a first step a general sufficient criterion for the presence of extra ion and electron currents due to nongyrotropic plasma conditions is derived. Then cases with antisymmetric magnetic and electric fields are considered. After establishing consistency of the criterion with the earlier case, the usefulness of this concept is illustrated in detail by two further particle simulations. The results indicate that the formation of nongyrotropic current sheets is a ubiquitous phenomenon for plasmas with antisymmetric fields that have evolved slowly from initial gyrotropic states. A fourth case concerns a plasma with a unidirectional magnetic field. Consistent with the general criterion, the observed final state is fluidlike in that it is approximately gyrotropic. Momentum balance is shown to include a contribution that results from accumulation of an off-diagonal pressure tensor component during the evolution. Heat flux also plays an important role.

  5. Plasmoid formation in the elongated current sheet during transient CHI on HIST

    NASA Astrophysics Data System (ADS)

    Nagata, Masayoshi; Fujita, Akihiro; Matsui, Takahiro; Kikuchi, Yusuke; Fukumoto, Naoyuki; Kanki, Takashi

    2016-10-01

    The Transient-Coaxial Helicity Injection (T-CHI) is a promising candidate for the non-inductive plasma start-up on Spherical Torus (ST). The problem of the flux closure in the T-CHI is important and related to understand the physics of fast magnetic reconnection. The recent MHD simulation (F. Ebrahimi and R. Raman, Phys. Rev. Lett. 114, 205003 (2015)) on T-CHI for NSTX predicts the formation and breakup of an elongated Sweet-Parker (S-P) current sheet and a transient to plasmoid instability. According to this simulation, the reconnection rate based on the plasmoid instability is faster than that by S-P model and becomes nearly independent of the Lundquist number S. In this meeting, we will present that the formation of multiple X-points and plasmoids has been observed in T-CHI start-up plasmas on HIST. The stronger external guide (toroidal) magnetic field makes plasma less compressible, leading to slower reconnection time and longer current sheet. The experimental observation shows that 2/3 plasmoids are generated in the elongated current sheet with the narrow width comparable to the ion skin depth or the ion sound gyro-radius. The small plasmoids develop to a large-scale flux structure due to a current inward diffusion during the decay phase.

  6. Tandem beta-enamino ester formation and cyclization with o-alkynyl anilines catalyzed by InBr3: efficient synthesis of beta-(N-indolyl)-alpha,beta-unsaturated esters.

    PubMed

    Murai, Kenichi; Hayashi, Shoko; Takaichi, Nobuhiro; Kita, Yasuyuki; Fujioka, Hiromichi

    2009-02-06

    A tandem reaction providing beta-(N-indolyl)-alpha,beta-unsaturated esters from beta-keto esters and o-alkynyl anilines was developed. Z-Alkenes were selectively formed due to the stability of the beta-enamino ester as an intermediate of the reaction. This reaction includes the intermolecular beta-enamino ester formation and intramolecular cyclization catalyzed by InBr(3).

  7. Interaction between two discontiguous chain segments from the beta-sheet of Escherichia coli thioredoxin suggests an initiation site for folding.

    PubMed

    Tasayco, M L; Fuchs, J; Yang, X M; Dyalram, D; Georgescu, R E

    2000-09-05

    The approach of comparing folding and folding/binding processes is exquisitely poised to narrow down the regions of the sequence that drive protein folding. We have dissected the small single alpha/beta domain of oxidized Escherichia coli thioredoxin (Trx) into three complementary fragments (N, residues 1-37; M, residues 38-73; and C, residues 74-108) to study them in isolation and upon recombination by far-UV CD and NMR spectroscopy. The isolated fragments show a minimum of ellipticity of ca. 197 nm in their far-UV CD spectra without concentration dependence, chemical shifts of H(alpha) that are close to the random coil values, and no medium- and long-range NOE connectivities in their three-dimensional NMR spectra. These fragments behave as disordered monomers. Only the far-UV CD spectra of binary or ternary mixtures that contain N- and C-fragments are different from the sum of their individual spectra, which is indicative of folding and/or binding of these fragments. Indeed, the cross-peaks corresponding to the rather hydrophobic beta(2) and beta(4) regions of the beta-sheet of Trx disappear from the (1)H-(15)N HSQC spectra of isolated labeled N- and C-fragments, respectively, upon addition of the unlabeled complementary fragments. The disappearing cross-peaks indicate interactions between the beta(2) and beta(4) regions, and their reappearance at lower temperatures indicates unfolding and/or dissociation of heteromers that are predominantly held by hydrophobic forces. Our results argue that the folding of Trx begins by zippering two discontiguous and rather hydrophobic chain segments (beta(2) and beta(4)) corresponding to neighboring strands of the native beta-sheet.

  8. An infrared spectroscopy approach to follow β-sheet formation in peptide amyloid assemblies

    NASA Astrophysics Data System (ADS)

    Seo, Jongcheol; Hoffmann, Waldemar; Warnke, Stephan; Huang, Xing; Gewinner, Sandy; Schöllkopf, Wieland; Bowers, Michael T.; von Helden, Gert; Pagel, Kevin

    2017-01-01

    Amyloidogenic peptides and proteins play a crucial role in a variety of neurodegenerative disorders such as Alzheimer's and Parkinson's disease. These proteins undergo a spontaneous transition from a soluble, often partially folded form, into insoluble amyloid fibrils that are rich in β-sheets. Increasing evidence suggests that highly dynamic, polydisperse folding intermediates, which occur during fibril formation, are the toxic species in the amyloid-related diseases. Traditional condensed-phase methods are of limited use for characterizing these states because they typically only provide ensemble averages rather than information about individual oligomers. Here we report the first direct secondary-structure analysis of individual amyloid intermediates using a combination of ion mobility spectrometry-mass spectrometry and gas-phase infrared spectroscopy. Our data reveal that oligomers of the fibril-forming peptide segments VEALYL and YVEALL, which consist of 4-9 peptide strands, can contain a significant amount of β-sheet. In addition, our data show that the more-extended variants of each oligomer generally exhibit increased β-sheet content.

  9. Interepithelial signaling with nephric duct is required for the formation of overlying coelomic epithelial cell sheet.

    PubMed

    Yoshino, Takashi; Saito, Daisuke; Atsuta, Yuji; Uchiyama, Chihiro; Ueda, Shinya; Sekiguchi, Kiyotoshi; Takahashi, Yoshiko

    2014-05-06

    In most organs of the body, epithelial tissues are supported by their own basement membrane and underlying stroma, the latter being regarded as a complex of amorphous cells, extracellular matrices, and soluble factors. We demonstrate here that an epithelial tube can serve as a component of stroma that supports the formation of epithelial cell sheet derived from a different origin. During development of the mesonephros in chicken embryos, the intermediate mesoderm (IMM), which contains the Wolffian duct (WD) and its associated tubules, is overlain by a sheet of epithelial cells derived from lateral plate (coelomic) mesoderm. We describe that in normal embryos, epitheliogenesis of IMM tubes and the adjacent coelomic cell sheet proceed in a coordinated manner. When the WD was surgically ablated, the overlying coelomic epithelium exhibited aberrant morphology accompanied by a punctated basement membrane. Furthermore, the WD-ablated coelomic epithelium became susceptible to latent external stress; electroporation of Rac1 resulted in epithelial-to-mesenchymal transitions (EMTs) within the coelomic epithelium. The distorted coelomic epithelium was rescued by implanting fibronectin-producing cells in place of the WD, suggesting that fibronectin provided by WD has an important role acting interepithelially. This notion was corroborated further by directly visualizing a translocation of EGFP-tagged fibronectin from fibronectin-producing to -receiving epithelia in vivo. Our findings provide a novel insight into interepithelial signaling that also might occur in adult tissues to protect against EMT and suggest a possible new target for anticancer therapeutic strategy.

  10. Formation and antimicrobial activity of complexes of beta-cyclodextrin and some antimycotic imidazole derivatives.

    PubMed

    Van Doorne, H; Bosch, E H; Lerk, C F

    1988-04-22

    Complex formation between beta-cyclodextrin and six antimycotic imidazole derivatives has been studied. The solubility of all drugs was increased in the presence of beta-cyclodextrin. The smallest increase (approx. 5-fold) was observed for miconazol, and the largest increase (approx. 160-fold) was observed for bifonazol. Apparent 1:1-complex constants were measured and found to decrease in the order: bifonazol greater than ketoconazol greater than tioconazol greater than miconazol greater than itraconazol greater than clotrimazol. The complexes appeared to possess a low, if any, antimicrobial activity. Measurement of inhibition zone sizes, with four test organisms was used to study the release of the antimycotic drugs from topical preparations. The antimycotic drugs were more readily released from topical preparations containing beta-cyclodextrin than from the same vehicles without beta-cyclodextrin. The rationale of beta-cyclodextrin addition to antimycotic topical preparations is discussed.

  11. Venus - Volcanism and rift formation in Beta Regio

    NASA Technical Reports Server (NTRS)

    Campbell, D. B.; Harmon, J. K.; Hine, A. A.; Head, J. W.

    1984-01-01

    A new high-resolution radar image of Beta Regio, a Venus highland area, confirms the presence of a major tectonic rift system and associated volcanic activity. The lack of identifiable impact craters, together with the apparent superposition of the Theia Mons volcanic structure on the rift system, suggest that at least some of the volcanic activity occurred in relatively recent geologic time. The presence of topographically similar highland areas elsewhere on Venus (Aphrodite Terra, Dali Chasma, and Diana Chasma) suggests that rifting and volcanism are significant processes on Venus.

  12. Affilin-novel binding molecules based on human gamma-B-crystallin, an all beta-sheet protein.

    PubMed

    Ebersbach, Hilmar; Fiedler, Erik; Scheuermann, Tanja; Fiedler, Markus; Stubbs, Milton T; Reimann, Carola; Proetzel, Gabriele; Rudolph, Rainer; Fiedler, Ulrike

    2007-09-07

    The concept of novel binding proteins as an alternative to antibodies has undergone rapid development and is now ready for practical use in a wide range of applications. Alternative binding proteins, based on suitable scaffolds with desirable properties, are selected from combinatorial libraries in vitro. Here, we describe an approach using a beta-sheet of human gamma-B-crystallin to generate a universal binding site through randomization of eight solvent-exposed amino acid residues selected according to structural and sequence analyses. Specific variants, so-called Affilin, have been isolated from a phage display library against a variety of targets that differ considerably in size and structure. The isolated Affilin variants can be produced in Escherichia coli as soluble proteins and have a high level of thermodynamic stability. The crystal structures of the human wild-type gamma-B-crystallin and a selected Affilin variant have been determined to 1.7 A and 2.0 A resolution, respectively. Comparison of the two molecules indicates that the human gamma-B-crystallin tolerates amino acid exchanges with no major structural change. We conclude that the intrinsically stable and easily expressed gamma-B-crystallin provides a suitable framework for the generation of novel binding molecules.

  13. Hierarchies, multiple energy barriers, and robustness govern the fracture mechanics of alpha-helical and beta-sheet protein domains.

    PubMed

    Ackbarow, Theodor; Chen, Xuefeng; Keten, Sinan; Buehler, Markus J

    2007-10-16

    The fundamental fracture mechanisms of biological protein materials remain largely unknown, in part, because of a lack of understanding of how individual protein building blocks respond to mechanical load. For instance, it remains controversial whether the free energy landscape of the unfolding behavior of proteins consists of multiple, discrete transition states or the location of the transition state changes continuously with the pulling velocity. This lack in understanding has thus far prevented us from developing predictive strength models of protein materials. Here, we report direct atomistic simulation that over four orders of magnitude in time scales of the unfolding behavior of alpha-helical (AH) and beta-sheet (BS) domains, the key building blocks of hair, hoof, and wool as well as spider silk, amyloids, and titin. We find that two discrete transition states corresponding to two fracture mechanisms exist. Whereas the unfolding mechanism at fast pulling rates is sequential rupture of individual hydrogen bonds (HBs), unfolding at slow pulling rates proceeds by simultaneous rupture of several HBs. We derive the hierarchical Bell model, a theory that explicitly considers the hierarchical architecture of proteins, providing a rigorous structure-property relationship. We exemplify our model in a study of AHs, and show that 3-4 parallel HBs per turn are favorable in light of the protein's mechanical and thermodynamical stability, in agreement with experimental findings that AHs feature 3.6 HBs per turn. Our results provide evidence that the molecular structure of AHs maximizes its robustness at minimal use of building materials.

  14. Current sheet formation in a 3D line-tied plasma

    NASA Astrophysics Data System (ADS)

    Zhou, Yao; Huang, Yi-Min; Qin, Hong; Bhattacharjee, Amitava

    2016-10-01

    Recently a variational integrator for ideal MHD in Lagrangian labeling has been developed by discretizing Newcomb's Lagrangian on a moving mesh using discretized exterior calculus. With the frozen-in equation built-in, the method is free of artificial reconnection, and therefore optimal for studying current sheet formation. Using this method, it is confirmed that the nonlinear solution to the ideal Hahm-Kulsrud-Taylor problem in 2D yields a singular current sheet. We identify it by showing that the equilibrium solution converges with increasing resolution, except where there is singularity. This approach is in contrast to previous studies which use diverging peak current density as sole evidence of current singularity. We then extend the problem to 3D line-tied geometry. The linear solution, which is singular in 2D, is found to be smooth, but pathological when the system is sufficiently long. Accordingly, the nonlinear solution turns out to be smooth for short systems, but tends to become more singular when the system length increases. A resolution to this problem can potentially settle the long-standing controversy over Parker's conjecture on the formation of current singularity in 3D line-tied geometry. This research was supported by the U.S. DOE under Contract No. DE-AC02-09CH11466.

  15. Beta-glycerophosphate accelerates RANKL-induced osteoclast formation in the presence of ascorbic acid.

    PubMed

    Noh, A Long Sae Mi; Yim, Mijung

    2011-03-01

    Despite numerous reports of the synergistic effects of beta-glycerophosphate and ascorbic acid in inducing the differentiation of osteoblasts, little is known about their roles in osteoclastic differentiation. Therefore, we investigated the effect of beta-glycerophosphate on osteoclastogenesis in the presence of ascorbic acid using primary mouse bone marrow cultures treated with macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor (NF)-kappaB ligand (RANKL). Beta-Glycerophosphate dose-dependently increased RANKL-induced osteoclast formation in the presence of ascorbic acid. This stimulatory effect was apparent when beta-glycerophosphate and ascorbic acid were only added during the late stages of the culture period, indicating that they influence later events in osteoclastic differentiation. While the combination of beta-glycerophosphate and ascorbic acid inhibited RANKL-stimulated activation of ERK and p38, and degradation of IkappaB, it increased the induction of c-Fos and NFATc1. In addition, beta-glycerophosphate and ascorbic acid together enhanced the induction of COX-2 following RANKL stimulation. Taken together, our data suggest that beta-glycerophosphate and ascorbic acid have synergistic effects on osteoclast formation, increasing RANKL-mediated induction of c-Fos, NFATc1 and COX-2 in osteoclast precursors.

  16. Formation and Degradation of Beta-casomorphins in Dairy Processing.

    PubMed

    Nguyen, Duc Doan; Johnson, Stuart Keith; Busetti, Francesco; Solah, Vicky Ann

    2015-01-01

    Milk proteins including casein are sources of peptides with bioactivity. One of these peptides is beta-casomorphin (BCM) which belongs to a group of opioid peptides formed from β-casein variants. Beta-casomorphin 7 (BCM7) has been demonstrated to be enzymatically released from the A1 or B β-casein variant. Epidemiological evidence suggests the peptide BCM 7 is a risk factor for development of human diseases, including increased risk of type 1 diabetes and cardiovascular diseases but this has not been thoroughly substantiated by research studies. High performance liquid chromatography coupled to UV-Vis and mass spectrometry detection as well as enzyme-linked immunosorbent assay (ELISA) has been used to analyze BCMs in dairy products. BCMs have been detected in raw cow's milk and human milk and a variety of commercial cheeses, but their presence has yet to be confirmed in commercial yoghurts. The finding that BCMs are present in cheese suggests they could also form in yoghurt, but be degraded during yoghurt processing. Whether BCMs do form in yoghurt and the amount of BCM forming or degrading at different processing steps needs further investigation and possibly will depend on the heat treatment and fermentation process used, but it remains an intriguing unknown.

  17. Penicillinase (beta-lactamase) formation by blue-green algae.

    PubMed

    Kushner, D J; Breuil, C

    1977-03-01

    Beta-Lactamase (penicillinase) activity was found in a number of strains of blue-green algea. In some cases, this enzyme permitted algae to overcome the inhibitory effects of penicillin. Production and localization of beta-lactamase were studied in a unicellular species, Coccochloris elabens (strain 7003), and in a filamentous, nitrogen-fixing Anabaena species (strain 7120). When cells were grown in a neutral medium with NaNO3 as N source, the pH rose during growth; at a pH of about 10, most of the enzyme was expressed equally well in intact or disrupted cells. If the pH was kept near neutrality during growth by gassing with CO2 in N2 or by growth under conditions of N2 fixation, the enzyme remained cell-bound and cryptic for most of the growth phase, being measurable only after cells were disrupted. The enzymes from strains 7003 and 7120 had greater activity on benzyl penicillin and other penicillins than on cephalosporins. Some differences were observed in the "substrate proliles" of penicillinases from the two strains against different penicillins.

  18. Formation and Degradation of Beta-casomorphins in Dairy Processing

    PubMed Central

    Nguyen, Duc Doan; Johnson, Stuart Keith; Busetti, Francesco; Solah, Vicky Ann

    2015-01-01

    Milk proteins including casein are sources of peptides with bioactivity. One of these peptides is beta-casomorphin (BCM) which belongs to a group of opioid peptides formed from β-casein variants. Beta-casomorphin 7 (BCM7) has been demonstrated to be enzymatically released from the A1 or B β-casein variant. Epidemiological evidence suggests the peptide BCM 7 is a risk factor for development of human diseases, including increased risk of type 1 diabetes and cardiovascular diseases but this has not been thoroughly substantiated by research studies. High performance liquid chromatography coupled to UV-Vis and mass spectrometry detection as well as enzyme–linked immunosorbent assay (ELISA) has been used to analyze BCMs in dairy products. BCMs have been detected in raw cow's milk and human milk and a variety of commercial cheeses, but their presence has yet to be confirmed in commercial yoghurts. The finding that BCMs are present in cheese suggests they could also form in yoghurt, but be degraded during yoghurt processing. Whether BCMs do form in yoghurt and the amount of BCM forming or degrading at different processing steps needs further investigation and possibly will depend on the heat treatment and fermentation process used, but it remains an intriguing unknown. PMID:25077377

  19. Repurposing doxycycline for synucleinopathies: remodelling of α-synuclein oligomers towards non-toxic parallel beta-sheet structured species

    PubMed Central

    González-Lizárraga, Florencia; Socías, Sergio B.; Ávila, César L.; Torres-Bugeau, Clarisa M.; Barbosa, Leandro R. S.; Binolfi, Andres; Sepúlveda-Díaz, Julia E.; Del-Bel, Elaine; Fernandez, Claudio O.; Papy-Garcia, Dulce; Itri, Rosangela; Raisman-Vozari, Rita; Chehín, Rosana N.

    2017-01-01

    Synucleinophaties are progressive neurodegenerative disorders with no cure to date. An attractive strategy to tackle this problem is repurposing already tested safe drugs against novel targets. In this way, doxycycline prevents neurodegeneration in Parkinson models by modulating neuroinflammation. However, anti-inflammatory therapy per se is insufficient to account for neuroprotection. Herein we characterise novel targets of doxycycline describing the structural background supporting its effectiveness as a neuroprotector at subantibiotic doses. Our results show that doxycycline reshapes α-synuclein oligomers into off-pathway, high-molecular-weight species that do not evolve into fibrils. Off-pathway species present less hydrophobic surface than on-pathway oligomers and display different β-sheet structural arrangement. These structural changes affect the α-synuclein ability to destabilize biological membranes, cell viability, and formation of additional toxic species. Altogether, these mechanisms could act synergically giving novel targets for repurposing this drug. PMID:28155912

  20. Repurposing doxycycline for synucleinopathies: remodelling of α-synuclein oligomers towards non-toxic parallel beta-sheet structured species.

    PubMed

    González-Lizárraga, Florencia; Socías, Sergio B; Ávila, César L; Torres-Bugeau, Clarisa M; Barbosa, Leandro R S; Binolfi, Andres; Sepúlveda-Díaz, Julia E; Del-Bel, Elaine; Fernandez, Claudio O; Papy-Garcia, Dulce; Itri, Rosangela; Raisman-Vozari, Rita; Chehín, Rosana N

    2017-02-03

    Synucleinophaties are progressive neurodegenerative disorders with no cure to date. An attractive strategy to tackle this problem is repurposing already tested safe drugs against novel targets. In this way, doxycycline prevents neurodegeneration in Parkinson models by modulating neuroinflammation. However, anti-inflammatory therapy per se is insufficient to account for neuroprotection. Herein we characterise novel targets of doxycycline describing the structural background supporting its effectiveness as a neuroprotector at subantibiotic doses. Our results show that doxycycline reshapes α-synuclein oligomers into off-pathway, high-molecular-weight species that do not evolve into fibrils. Off-pathway species present less hydrophobic surface than on-pathway oligomers and display different β-sheet structural arrangement. These structural changes affect the α-synuclein ability to destabilize biological membranes, cell viability, and formation of additional toxic species. Altogether, these mechanisms could act synergically giving novel targets for repurposing this drug.

  1. Identification and characterization of the antimicrobial peptide corresponding to C-terminal beta-sheet domain of tenecin 1, an antibacterial protein of larvae of Tenebrio molitor.

    PubMed

    Lee, K H; Hong, S Y; Oh, J E; Kwon, M; Yoon, J H; Lee, J; Lee, B L; Moon, H M

    1998-08-15

    An active fragment was identified from tenecin 1, an antibacterial protein belonging to the insect defensin family, by synthesizing the peptides corresponding to the three regions of tenecin 1. Only the fragment corresponding to the C-terminal beta-sheet domain showed activity against fungi as well as Gram-positive and Gram-negative bacteria, whereas tenecin 1, the native protein, showed activity only against Gram-positive bacteria. CD spectra indicated that each fragment in a membrane-mimetic environment might adopt a secondary structure corresponding to its region in the protein. The leakage of dye from liposomes induced by this fragment suggested that this fragment acts on the membrane of pathogens as a primary mode of action. A comparison between the structure and the activity of each fragment indicated that a net positive charge was a prerequisite factor for activity. To the best of our knowledge this is the first report in which the fragment corresponding to the beta-sheet region in antibacterial proteins, which consists of alpha-helical and beta-sheet regions, has been identified as a primary active fragment.

  2. Effect of secondary structure on the potential of mean force for poly-L-lysine in the alpha-Helix and beta-sheet conformations

    SciTech Connect

    Grigsby, J.J.; Blanch, H.W.; Prausnitz, J.M.

    2001-10-30

    Because poly-L-lysine (PLL) can exist in the {alpha}-helix or {beta}-sheet conformation depending on solution preparation and solution conditions, PLL is a suitable candidate to probe the dependence of protein interactions on secondary structure. The osmotic second virial coefficient and weight-average molecular weight are reported from low-angle laser-light scattering measurements for PLL as a function of NaCl concentration, pH, and {alpha}-helix or {beta}-sheet content. Interactions between PLL molecules become more attractive as salt concentration increases due to screening of PLL charge by salt ions and at low salt concentration become more attractive as pH increases due to decreased net charge on PLL. The experimental results show that interactions are stronger for the {beta}-sheet conformation than for the {alpha}-helix conformation. A spherically-symmetric model for the potential of mean force is used to account for specific interactions not described by DLVO theory and to show how differences in secondary structure affect PLL interactions.

  3. Existing Data Format for Two-Parameter Beta-Gamma Histograms for Radioxenon

    SciTech Connect

    TW Bowyer; TR Heimbigner; JI McIntyre; AD McKinnon; PL Reeder; E Wittinger

    1999-03-23

    There is a need to establish a commonly acceptable format for storing beta-gated coincidence data for stations in the International Monitoring System (IMS) for the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The current aerosol RMS type data format is not applicable for radioxenon in that the current format contains implicit assumptions specific to conventional gamma-ray spectrometry. Some assumptions in the current RMS format are not acceptable for the beta-gated spectra expected from the U.S. Department of Energy PNNL Automated Radioxenon Sampler-Analyzer (ARSA) and other similar systems under use or development from various countries. The RMS data format is not generally applicable for radioxenon measurements in the CTBT for one or more of the following main reasons: 1) The RMS format does not currently support 2-dimensional data. That is, the RMS data format is setup for a simple l-dimensional gamma-ray energy histogram. Current data available from the ARSA system and planned for other radioxenon monitors includes spectral information from gamma-rays and betas/conversion electrons. It is worth noting that the beta/conversion electron energy information will be used to separate the contributions from the different radioxenons. 2) The RMS data format assumes that the conversion between counts and activity can be calculated based (in part) on a simple calibration curve (detector efficiency curve) that depends only on energy of the gamma-ray. In the case of beta-gated gamma-ray spectra and for 2-dimensional spectra, there are generally two detector calibration curves that must be convoluted, the lower energy cutoff for the betas must be considered, and the energy acceptance window must be taken into account to convert counts into activity. . 3) The RMS format has header information that contains aerosol-specific information that allows the activity (Bq) calculated to be converted into a concentration (Bq/SCM). This calculation is performed by dividing the

  4. Bone formation in transforming growth factor beta-1-coated porous poly(propylene fumarate) scaffolds.

    PubMed

    Vehof, Johan W M; Fisher, John P; Dean, David; van der Waerden, Jan-Paul C M; Spauwen, Paul H M; Mikos, Antonios G; Jansen, John A

    2002-05-01

    This study determined the bone growth into pretreated poly(propylene fumarate) (PPF) scaffolds implanted into a subcritical size, rabbit cranial defect. PPF scaffolds were constructed by using a photocrosslinking-porogen leaching technique. These scaffolds were then either prewetted (PPF-Pw), treated with RF glow-discharge (PPF-Gd), coated with fibronectin (PPF-Fn), or coated with rhTGF-beta1 (PPF-TGF-beta1). One of each scaffold type was then placed into the cranium of nine rabbits. The rabbits were sacrificed after 8 weeks, and the scaffolds were retrieved for histological analysis. The most bone formation was present in the PPF-TGF-beta1 implants; the newly formed bone had a trabecular appearance together with bone marrow-like tissue. Little or no bone formation was observed in implants without rhTGF-beta1. These histological findings were confirmed by image analysis. Bone surface area, bone area percentage, pore fill percentage, and pore area percentage were significantly higher in the rhTGF-beta1-coated implants than in the noncoated implants. No statistical difference was seen between the PPF-Fn, PPF-Pw, or PPF-Gd scaffolds for these parameters. Quadruple fluorochrome labeling showed that in PPF-TGF-beta1 implants bone formation mainly started in the interior of a pore and proceeded toward the scaffold. We conclude that (a) PPF-TGF-beta1 scaffolds can indeed adequately induce bone formation in porous PPF, and (b) PPF scaffolds prepared by the photocrosslinking-porogen leaching technique are good candidates for the creation of bone graft substitutes.

  5. High-Resolution Structure of a Self-Assembly-Competent Form of a Hydrophobic Peptide Captured in a Soluble [beta]-Sheet Scaffold

    SciTech Connect

    Makabe, Koki; Biancalana, Matthew; Yan, Shude; Tereshko, Valentina; Gawlak, Grzegorz; Miller-Auer, Hélène; Meredith, Stephen C.; Koide, Shohei

    2010-02-08

    {beta}-Rich self-assembly is a major structural class of polypeptides, but still little is known about its atomic structures and biophysical properties. Major impediments for structural and biophysical studies of peptide self-assemblies include their insolubility and heterogeneous composition. We have developed a model system, termed peptide self-assembly mimic (PSAM), based on the single-layer {beta}-sheet of Borrelia outer surface protein A. PSAM allows for the capture of a defined number of self-assembly-like peptide repeats within a water-soluble protein, making structural and energetic studies possible. In this work, we extend our PSAM approach to a highly hydrophobic peptide sequence. We show that a penta-Ile peptide (Ile{sub 5}), which is insoluble and forms {beta}-rich self-assemblies in aqueous solution, can be captured within the PSAM scaffold in a form capable of self-assembly. The 1.1-{angstrom} crystal structure revealed that the Ile{sub 5} stretch forms a highly regular {beta}-strand within this flat {beta}-sheet. Self-assembly models built with multiple copies of the crystal structure of the Ile5 peptide segment showed no steric conflict, indicating that this conformation represents an assembly-competent form. The PSAM retained high conformational stability, suggesting that the flat {beta}-strand of the Ile{sub 5} stretch primed for self-assembly is a low-energy conformation of the Ile{sub 5} stretch and rationalizing its high propensity for self-assembly. The ability of the PSAM to 'solubilize' an otherwise insoluble peptide stretch suggests the potential of the PSAM approach to the characterization of self-assembling peptides.

  6. The digital geologic map of Colorado in ARC/INFO format, Part C. Explanation sheet database

    USGS Publications Warehouse

    Green, Gregory N.

    1992-01-01

    This geologic map was prepared as a part of a study of digital methods and techniques as applied to complex geologic maps. The geologic map was digitized from the original scribe sheets used to prepare the published Geologic Map of Colorado (Tweto 1979). Consequently the digital version is at 1:500,000 scale using the Lambert Conformal Conic map projection parameters of the state base map. Stable base contact prints of the scribe sheets were scanned on a Tektronix 4991 digital scanner. The scanner automatically converts the scanned image to an ASCII vector format. These vectors were transferred to a VAX minicomputer, where they were then loaded into ARC/INFO. Each vector and polygon was given attributes derived from the original 1979 geologic map. This database was developed on a MicroVAX computer system using VAX V 5.4 nd ARC/INFO 5.0 software. UPDATE: April 1995, The update was done solely for the purpose of adding the abilitly to plot to an HP650c plotter. Two new ARC/INFO plot AMLs along with a lineset and shadeset for the HP650C design jet printer have been included. These new files are COLORADO.650, INDEX.650, TWETOLIN.E00 and TWETOSHD.E00. These files were created on a UNIX platform with ARC/INFO 6.1.2. Updated versions of INDEX.E00, CONTACT.E00, LINE.E00, DECO.E00 and BORDER.E00 files that included the newly defined HP650c items are also included. * Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Descriptors: The Digital Geologic Map of Colorado in ARC/INFO Format Open-File Report 92-050

  7. Hazard Communication Standard for Chemical Labels and Safety Data Sheets In GHS Format

    EPA Pesticide Factsheets

    This fact sheet provides an overview of the required contents of Safety Data Sheets (SDSs) and chemical hazard labels, and includes tips on how these materials can be used to better protect health and the environment.

  8. Calcofluor fluorescence assay for wort beta-glucan in a microplate format

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The widely-used fluorescent (Calcofluor) flow injection analysis method for determining the concentrations of beta-glucans in Congress worts from barley malts is adapted to microplate format. Adaptation of the Calcofluor assay to use widely available fluorescent microplate readers makes the assay m...

  9. Phosphoinositide 3-kinase p85beta regulates invadopodium formation

    PubMed Central

    Cariaga-Martínez, Ariel E.; Cortés, Isabel; García, Esther; Pérez-García, Vicente; Pajares, María J.; Idoate, Miguel A.; Redondo-Muñóz, Javier; Antón, Inés M.; Carrera, Ana C.

    2014-01-01

    ABSTRACT The acquisition of invasiveness is characteristic of tumor progression. Numerous genetic changes are associated with metastasis, but the mechanism by which a cell becomes invasive remains unclear. Expression of p85β, a regulatory subunit of phosphoinositide-3-kinase, markedly increases in advanced carcinoma, but its mode of action is unknown. We postulated that p85β might facilitate cell invasion. We show that p85β localized at cell adhesions in complex with focal adhesion kinase and enhanced stability and maturation of cell adhesions. In addition, p85β induced development at cell adhesions of an F-actin core that extended several microns into the cell z-axis resembling the skeleton of invadopodia. p85β lead to F-actin polymerization at cell adhesions by recruiting active Cdc42/Rac at these structures. In accordance with p85β function in invadopodium-like formation, p85β levels increased in metastatic melanoma and p85β depletion reduced invadopodium formation and invasion. These results show that p85β enhances invasion by inducing cell adhesion development into invadopodia-like structures explaining the metastatic potential of tumors with increased p85β levels. PMID:25217619

  10. Integrin alpha6beta1-laminin interactions regulate early myotome formation in the mouse embryo.

    PubMed

    Bajanca, Fernanda; Luz, Marta; Raymond, Karine; Martins, Gabriel G; Sonnenberg, Arnoud; Tajbakhsh, Shahragim; Buckingham, Margaret; Thorsteinsdóttir, Sólveig

    2006-05-01

    We addressed the potential role of cell-laminin interactions during epaxial myotome formation in the mouse embryo. Assembly of the myotomal laminin matrix occurs as epaxial myogenic precursor cells enter the myotome. Most Myf5-positive and myogenin-negative myogenic precursor cells localise near assembled laminin, while myogenin-expressing cells are located either away from this matrix or in areas where it is being assembled. In Myf5(nlacZ/nlacZ) (Myf5-null) embryos, laminin, collagen type IV and perlecan are present extracellularly near myogenic precursor cells, but do not form a basement membrane and cells are not contained in the myotomal compartment. Unlike wild-type myogenic precursor cells, Myf5-null cells do not express the alpha6beta1 integrin, a laminin receptor, suggesting that integrin alpha6beta1-laminin interactions are required for myotomal laminin matrix assembly. Blocking alpha6beta1-laminin binding in cultured wild-type mouse embryo explants resulted in dispersion of Myf5-positive cells, a phenotype also seen in Myf5(nlacZ/nlacZ) embryos. Furthermore, inhibition of alpha6beta1 resulted in an increase in Myf5 protein and ectopic myogenin expression in dermomyotomal cells, suggesting that alpha6beta1-laminin interactions normally repress myogenesis in the dermomyotome. We conclude that Myf5 is required for maintaining alpha6beta1 expression on myogenic precursor cells, and that alpha6beta1 is necessary for myotomal laminin matrix assembly and cell guidance into the myotome. Engagement of laminin by alpha6beta1 also plays a role in maintaining the undifferentiated state of cells in the dermomyotome prior to their entry into the myotome.

  11. Nonlinear evolution of three-dimensional instabilities of thin and thick electron scale current sheets: Plasmoid formation and current filamentation

    SciTech Connect

    Jain, Neeraj; Büchner, Jörg

    2014-07-15

    Nonlinear evolution of three dimensional electron shear flow instabilities of an electron current sheet (ECS) is studied using electron-magnetohydrodynamic simulations. The dependence of the evolution on current sheet thickness is examined. For thin current sheets (half thickness =d{sub e}=c/ω{sub pe}), tearing mode instability dominates. In its nonlinear evolution, it leads to the formation of oblique current channels. Magnetic field lines form 3-D magnetic spirals. Even in the absence of initial guide field, the out-of-reconnection-plane magnetic field generated by the tearing instability itself may play the role of guide field in the growth of secondary finite-guide-field instabilities. For thicker current sheets (half thickness ∼5 d{sub e}), both tearing and non-tearing modes grow. Due to the non-tearing mode, current sheet becomes corrugated in the beginning of the evolution. In this case, tearing mode lets the magnetic field reconnect in the corrugated ECS. Later thick ECS develops filamentary structures and turbulence in which reconnection occurs. This evolution of thick ECS provides an example of reconnection in self-generated turbulence. The power spectra for both the thin and thick current sheets are anisotropic with respect to the electron flow direction. The cascade towards shorter scales occurs preferentially in the direction perpendicular to the electron flow.

  12. Concentration-dependent reversible self-oligomerization of serum albumins through intermolecular β-sheet formation.

    PubMed

    Bhattacharya, Arpan; Prajapati, Roopali; Chatterjee, Surajit; Mukherjee, Tushar Kanti

    2014-12-16

    Proteins inside a cell remain in highly crowded environments, and this often affects their structure and activity. However, most of the earlier studies involving serum albumins were performed under dilute conditions, which lack biological relevance. The effect of protein-protein interactions on the structure and properties of serum albumins at physiological conditions have not yet been explored. Here, we report for the first time the effect of protein-protein and protein-crowder interactions on the structure and stability of two homologous serum albumins, namely, human serum albumin (HSA) and bovine serum albumin (BSA), at physiological conditions by using spectroscopic techniques and scanning electron microscopy (SEM). Concentration-dependent self-oligomerization and subsequent structural alteration of serum albumins have been explored by means of fluorescence and circular dichroism spectroscopy at pH 7.4. The excitation wavelength (λex) dependence of the intrinsic fluorescence and the corresponding excitation spectra at each emission wavelength indicate the presence of various ground state oligomers of serum albumins in the concentration range 10-150 μM. Circular dichroism and thioflavin T binding assay revealed formation of intermolecular β-sheet rich interfaces at high protein concentration. Excellent correlations have been observed between β-sheet content of both the albumins and fluorescence enhancement of ThT with protein concentrations. SEM images at a concentration of 150 μM revealed large dispersed self-oligomeric states with sizes vary from 330 to 924 nm and 260 to 520 nm for BSA and HSA, respectively. The self-oligomerization of serum albumins is found to be a reversible process; upon dilution, these oligomers dissociate into a native monomeric state. It has also been observed that synthetic macromolecular crowder polyethylene glycol (PEG 200) stabilizes the self-associated state of both the albumins which is contrary to expectations that the

  13. Differential effects of ongoing EEG beta and theta power on memory formation

    PubMed Central

    Scholz, Sebastian; Schneider, Signe Luisa

    2017-01-01

    Recently, elevated ongoing pre-stimulus beta power (13–17 Hz) at encoding has been associated with subsequent memory formation for visual stimulus material. It is unclear whether this activity is merely specific to visual processing or whether it reflects a state facilitating general memory formation, independent of stimulus modality. To answer that question, the present study investigated the relationship between neural pre-stimulus oscillations and verbal memory formation in different sensory modalities. For that purpose, a within-subject design was employed to explore differences between successful and failed memory formation in the visual and auditory modality. Furthermore, associative memory was addressed by presenting the stimuli in combination with background images. Results revealed that similar EEG activity in the low beta frequency range (13–17 Hz) is associated with subsequent memory success, independent of stimulus modality. Elevated power prior to stimulus onset differentiated successful from failed memory formation. In contrast, differential effects between modalities were found in the theta band (3–7 Hz), with an increased oscillatory activity before the onset of later remembered visually presented words. In addition, pre-stimulus theta power dissociated between successful and failed encoding of associated context, independent of the stimulus modality of the item itself. We therefore suggest that increased ongoing low beta activity reflects a memory promoting state, which is likely to be moderated by modality-independent attentional or inhibitory processes, whereas high ongoing theta power is suggested as an indicator of the enhanced binding of incoming interlinked information. PMID:28192459

  14. Formation of {beta}-hydroxycarbonyls from the OH radical-initiated reactions of selected alkenes

    SciTech Connect

    Aschmann, S.M.; Arey, J.; Atkinson, R.

    2000-05-01

    {beta}-Hydroxycarbonyls can be formed from the gas-phase reactions of alkenes with the OH radical, both in the presence and in the absence of NO. To date, because of analytical difficulties, few data have been reported for the formation of this class of compound from the reactions of the OH radical with alkenes. The authors have determined that {beta}-hydroxy-ketones can be readily analyzed by gas chromatography, and in this work they have shown that in 1 atm of air the {beta}-hydroxyalkoxy radicals formed in the reactions of the OH radical with trans-2-butene, trans-3-hexene, 1-butene, and {alpha}-pinene in the presence of NO primarily decompose rather than react with O{sub 2}. Rate constant ratios k{sub d}/k{sub 0{sub 2}} (or lower limits thereof), where k{sub d} and k{sub 0{sub 2}} are respectively the rate constants for the decomposition and the reaction with 0{sub 2} of the intermediate {beta}-hydroxyalkoxy radicals, have been obtained for the reactions of the CH{sub 3}CH(O)CH-(OH)CH{sub 3}, CH{sub 3}CH{sub 2}CH(O)CH{sub 2}OH, and CH{sub 3}CH{sub 2}CH(O)CH(OH)CH{sub 2}-CH{sub 3} radicals at 296 {+-} 2 K and atmospheric pressure. Using the O{sub 3} reactions with the alkenes to generate OH radicals, the reactions of the OH radical to generate OH radicals, the reactions of the OH radical with trans-2-butene, trans-3-hexene, and {alpha}-pinene in the absence of NO lead to the formation of the expected {beta}-hydroxycarbonyls and (at least for trans-2-butene) the {alpha},{beta}-diol.

  15. Mutations that affect coenzyme binding and dimer formation of fungal 17beta-hydroxysteroid dehydrogenase.

    PubMed

    Brunskole, Mojca; Kristan, Katja; Stojan, Jure; Rizner, Tea Lanisnik

    2009-03-25

    The 17beta-hydroxysteroid dehydrogenase from the fungus Cochliobolus lunatus (17beta-HSDcl) is an NADPH-dependent member of the short-chain dehydrogenase/reductase superfamily, and it functions as a dimer that is composed of two identical subunits. By constructing the appropriate mutants, we have examined the M204 residue that is situated in the coenzyme binding pocket, for its role in the binding of the coenzyme NADP(H). We have also studied the importance of hydrophobic interactions through F124, F132, F133 and F177 for 17beta-HSDcl dimer formation. The M204G substitution decreased the catalytic efficiency of 17beta-HSDcl, suggesting that M204 sterically coerces the nicotinamide moiety of the coenzyme into the appropriate position for further hydride transfer. Phenylalanine substitutions introduced at the dimer interface produced inactive aggregates and oligomers with high molecular masses, suggesting that these hydrophobic interactions have important roles in the formation of the active dimer.

  16. Formation of a very thin current sheet in the near-earth magnetotail and the explosive growth phase of substorms

    NASA Technical Reports Server (NTRS)

    Lee, L. C.; Zhang, L.; Choe, G. S.; Cai, H. J.

    1995-01-01

    A magnetofricional method is used to construct two-dimensional MHD equilibria of the Earth's magnetosphere for a given distribution of entropy functions(S = pV(exp gamma), where p is the plasma pressure and V is the tube volume per unit magnetic flux. It is found that a very thin current sheet with B (sub zeta) is less than 0.5 nu T and thickness less than 1000 km can be formed in the near-earth magnetotail (x is approximately -8 to -20R(sub e) during the growth phase of substorm. The tail current sheets are found to become thinner as the entropy or the entropy gradient increases. It is suggested that the new entropy anti-diffusion instability associated with plasma transport across field lines leads to magnetic field dipolarization and accelerates the formation of thin current sheet, which may explain the observed explosive growth phase of substorms.

  17. Inducing β-Sheets Formation in Synthetic Spider Silk Fibers by Aqueous Post-Spin Stretching

    PubMed Central

    Hinman, Michael B.; Holland, Gregory P.; Yarger, Jeffery L.; Lewis, Randolph V.

    2012-01-01

    As a promising biomaterial with numerous potential applications, various types of synthetic spider silk fibers have been produced and studied in an effort to produce manmade fibers with mechanical and physical properties comparable to those of native spider silk. In this study, two recombinant proteins based on Nephila clavipes Major ampullate Spidroin 1 (MaSp1) consensus repeat sequence were expressed and spun into fibers. Mechanical test results showed that fiber spun from the higher molecular weight protein had better overall mechanical properties (70 KD versus 46 KD), whereas postspin stretch treatment in water helped increase fiber tensile strength significantly. Carbon-13 solid-state NMR studies of those fibers further revealed that the postspin stretch in water promoted protein molecule rearrangement and the formation of β-sheets in the polyalanine region of the silk. The rearrangement correlated with improved fiber mechanical properties and indicated that postspin stretch is key to helping the spider silk proteins in the fiber form correct secondary structures, leading to better quality fibers. PMID:21574576

  18. Repetitive formation and decay of current sheets in magnetic loops: An origin of diverse magnetic structures

    SciTech Connect

    Kumar, Dinesh; Bhattacharyya, R.; Smolarkiewicz, P. K.

    2015-01-15

    In this work, evolution of an incompressible, thermally homogeneous, infinitely conducting, viscous magnetofluid is numerically explored as the fluid undergoes repeated events of magnetic reconnection. The initial magnetic field is constructed by a superposition of two linear force-free fields and has similar morphology as the magnetic loops observed in the solar corona. The results are presented for computations with three distinct sets of footpoint geometries. To onset reconnection, we rely on numerical model magnetic diffusivity, in the spirit of implicit large eddy simulation. It is generally expected that in a high Lundquist number fluid, repeated magnetic reconnections are ubiquitous and hence can lead to a host of magnetic structures with considerable observational importance. In particular, the simulations presented here illustrate formations of magnetic islands, rotating magnetic helices and rising flux ropes—depending on the initial footpoint geometry but through the common process of repeated magnetic reconnections. Further, we observe the development of extended current sheets in two case studies, where the footpoint reconnections generate favorable dynamics.

  19. Optimal heating condition of mouthguard sheet in vacuum-pressure formation: part 2 Olefin-based thermoplastic elastomer.

    PubMed

    Takahashi, Mutsumi; Koide, Kaoru

    2016-04-01

    The purposes of this study were to clarify the suitable heating conditions during vacuum-pressure formation of olefin copolymer sheets and to examine the sheet temperature at molding and the thickness of the molded mouthguard. Mouthguards were fabricated using 4.0-mm-thick olefin copolymer sheets utilizing a vacuum-pressure forming device, and then, 10 s of vacuum forming and 2 min of compression molding were applied. Three heating conditions were investigated. They were, defined by the degree of sagging observed at the center of the softened sheet (10, 15, or 20 mm lower than the clamp (H-10, H-15, or H-20, respectively)). The working model was trimmed to the height of 20 mm at the maxillary central incisor and 15 mm at the mesiobuccal cusp of the maxillary first molar. The temperature on both the directly heated and the non-heated surfaces of the mouthguard sheet was measured by the radiation thermometer for each condition. The thickness of mouthguard sheets after fabrication was determined for the incisal portion (incisal edge and labial surface) and molar portion (cusp and buccal surface), and dimensional measurements were obtained using a measuring device. Differences in the thickness due to the heating condition of the sheets were analyzed by one-way analysis of variance and Bonferroni's multiple comparison tests. The temperature difference between the heated and non-heated surfaces was highest under H-10. Sheet temperature under H-15 and H-20 was almost the same. The thickness differences were noted at incisal edge, cusp, and buccal surface, and H-15 was the greatest. This study demonstrated that heating of the sheet resulting in sag of 15 mm or more was necessary for sufficient softening of the sheet and that the mouthguard thickness decreased with increased sag. In conclusion, sag of 15 mm can be recommended as a good indicator of appropriate molding timing for this material.

  20. Current sheet formation in quasi-separatrix layers and hyperbolic flux tubes

    NASA Astrophysics Data System (ADS)

    Aulanier, G.; Pariat, E.; Démoulin, P.

    2005-12-01

    In 3D magnetic field configurations, quasi-separatrix layers (QSLs) are defined as volumes in which field lines locally display strong gradients of connectivity. Considering QSLs both as the preferential locations for current sheet development and magnetic reconnection, in general, and as a natural model for solar flares and coronal heating, in particular, has been strongly debated issues over the past decade. In this paper, we perform zero-β resistive MHD simulations of the development of electric currents in smooth magnetic configurations which are, strictly speaking, bipolar though they are formed by four flux concentrations, and whose potential fields contain QSLs. The configurations are driven by smooth and large-scale sub-Alfvénic footpoint motions. Extended electric currents form naturally in the configurations, which evolve through a sequence of quasi non-linear force-free equilibria. Narrow current layers also develop. They spontaneously form at small scales all around the QSLs, whatever the footpoint motions are. For long enough motions, the strongest currents develop where the QSLs are the thinnest, namely at the Hyperbolic Flux Tube (HFT), which generalizes the concept of separator. These currents progressively take the shape of an elongated sheet, whose formation is associated with a gradual steepening of the magnetic field gradients over tens of Alfvén times, due to the different motions applied to the field lines which pass on each side of the HFT. Our model then self-consistently accounts for the long-duration energy storage prior to a flare, followed by a switch-on of reconnection when the currents reach the dissipative scale at the HFT. In configurations whose potential fields contain broader QSLs, when the magnetic field gradients reach the dissipative scale, the currents at the HFT reach higher magnitudes. This implies that major solar flares which are not related to an early large-scale ideal instability, must occur in regions whose

  1. The three-dimensional structural surface of two beta-sheet scorpion toxins mimics that of an alpha-helical dihydropyridine receptor segment.

    PubMed Central

    Green, Daniel; Pace, Suzi; Curtis, Suzanne M; Sakowska, Magdalena; Lamb, Graham D; Dulhunty, Angela F; Casarotto, Marco G

    2003-01-01

    An alpha-helical II-III loop segment of the dihydropyridine receptor activates the ryanodine receptor calcium-release channel. We describe a novel manipulation in which this agonist's activity is increased by modifying its surface structure to resemble that of a toxin molecule. In a unique system, native beta-sheet scorpion toxins have been reported to activate skeletal muscle ryanodine receptor calcium channels with high affinity by binding to the same site as the lower-affinity alpha-helical dihydropyridine receptor segment. We increased the alignment of basic residues in the alpha-helical peptide to mimic the spatial orientation of active residues in the scorpion toxin, with a consequent 2-20-fold increase in the activity of the alpha-helical peptide. We hypothesized that, like the native peptide, the modified peptide and the scorpion toxin may bind to a common site. This was supported by (i) similar changes in ryanodine receptor channel gating induced by the native or modified alpha-helical peptide and the beta-sheet toxin, a 10-100-fold reduction in channel closed time, with a < or = 2-fold increase in open dwell time and (ii) a failure of the toxin to further activate channels activated by the peptides. These results suggest that diverse structural scaffolds can present similar conformational surface properties to target common receptor sites. PMID:12429019

  2. Water network dynamics at the critical moment of a peptide's beta-turn formation: a molecular dynamics study.

    PubMed

    Karvounis, George; Nerukh, Dmitry; Glen, Robert C

    2004-09-08

    All-atom molecular dynamics simulations for a single molecule of Leu-Enkephalin in aqueous solution have been used to study the role of the water network during the formation of beta-turns. We give a detailed account of the intramolecular hydrogen bonding, the water-peptide hydrogen bonding, and the orientation and residence times of water molecules focusing on the short critical periods of transition to the stable beta-turns. These studies suggest that, when intramolecular hydrogen bonding between the first and fourth residue of the beta-turn is not present, the disruption of the water network and the establishment of water bridges constitute decisive factors in the formation and stability of the beta-turn. Finally, we provide possible explanations and mechanisms for the formations of different kinds of beta-turns.

  3. Protein Secondary Structures (alpha-helix and beta-sheet) at a Cellular Levle and Protein Fractions in Relation to Rumen Degradation Behaviours of Protein: A New Approach

    SciTech Connect

    Yu,P.

    2007-01-01

    Studying the secondary structure of proteins leads to an understanding of the components that make up a whole protein, and such an understanding of the structure of the whole protein is often vital to understanding its digestive behaviour and nutritive value in animals. The main protein secondary structures are the {alpha}-helix and {beta}-sheet. The percentage of these two structures in protein secondary structures influences protein nutritive value, quality and digestive behaviour. A high percentage of {beta}-sheet structure may partly cause a low access to gastrointestinal digestive enzymes, which results in a low protein value. The objectives of the present study were to use advanced synchrotron-based Fourier transform IR (S-FTIR) microspectroscopy as a new approach to reveal the molecular chemistry of the protein secondary structures of feed tissues affected by heat-processing within intact tissue at a cellular level, and to quantify protein secondary structures using multicomponent peak modelling Gaussian and Lorentzian methods, in relation to protein digestive behaviours and nutritive value in the rumen, which was determined using the Cornell Net Carbohydrate Protein System. The synchrotron-based molecular chemistry research experiment was performed at the National Synchrotron Light Source at Brookhaven National Laboratory, US Department of Energy. The results showed that, with S-FTIR microspectroscopy, the molecular chemistry, ultrastructural chemical make-up and nutritive characteristics could be revealed at a high ultraspatial resolution ({approx}10 {mu}m). S-FTIR microspectroscopy revealed that the secondary structure of protein differed between raw and roasted golden flaxseeds in terms of the percentages and ratio of {alpha}-helixes and {beta}-sheets in the mid-IR range at the cellular level. By using multicomponent peak modelling, the results show that the roasting reduced (P <0.05) the percentage of {alpha}-helixes (from 47.1% to 36.1%: S

  4. Observations of the Formation, Development, and Structure of a Current Sheet in an Eruptive Solar Flare

    NASA Astrophysics Data System (ADS)

    Seaton, Daniel B.; Bartz, Allison E.; Darnel, Jonathan M.

    2017-02-01

    We present Atmospheric Imaging Assembly observations of a structure we interpret as a current sheet associated with an X4.9 flare and coronal mass ejection that occurred on 2014 February 25 in NOAA Active Region 11990. We characterize the properties of the current sheet, finding that the sheet remains on the order of a few thousand kilometers thick for much of the duration of the event and that its temperature generally ranged between 8 and 10 MK. We also note the presence of other phenomena believed to be associated with magnetic reconnection in current sheets, including supra-arcade downflows and shrinking loops. We estimate that the rate of reconnection during the event was MA ≈ 0.004–0.007, a value consistent with model predictions. We conclude with a discussion of the implications of this event for reconnection-based eruption models.

  5. A study of the formation and dynamics of the Earth's plasma sheet using ion composition data

    NASA Technical Reports Server (NTRS)

    Lennartsson, O. W.

    1994-01-01

    Over two years of data from the Lockheed Plasma Composition Experiment on the ISEE 1 spacecraft, covering ion energies between 100 eV/e and about 16 keV/e, have been analyzed in an attempt to extract new information about three geophysical issues: (1) solar wind penetration of the Earth's magnetic tail; (2) relationship between plasma sheet and tail lobe ion composition; and (3) possible effects of heavy terrestrial ions on plasma sheet stability.

  6. Multifunctional acid formation from the gas-phase ozonolysis of beta-pinene.

    PubMed

    Ma, Yan; Marston, George

    2008-10-28

    The gas-phase ozonolysis of beta-pinene was studied in static chamber experiments, using gas chromatography coupled to mass spectrometric and flame ionisation detection to separate and detect products. A range of multifunctional organic acids-including pinic acid, norpinic acid, pinalic-3-acid, pinalic-4-acid, norpinalic acid and OH-pinalic acid-were identified in the condensed phase after derivatisation. Formation yields for these products under systematically varying reaction conditions (by adding different OH radical scavengers and Criegee intermediate scavengers) were investigated and compared with those observed from alpha-pinene ozonolysis, allowing detailed information on product formation mechanisms to be elucidated. In addition, branching ratios for the initial steps of the reaction were inferred from quantitative measurements of primary carbonyl formation. Atmospheric implications of this work are discussed.

  7. Nanofibers formed through pi...pi stacking of the complexes of glucosyl-C2-salicyl-imine and phenylalanine: characterization by microscopy, modeling by molecular mechanics, and interaction by alpha-helical and beta-sheet proteins.

    PubMed

    Acharya, Amitabha; Ramanujam, Balaji; Mitra, Atanu; Rao, Chebrolu P

    2010-07-27

    This paper deals with the self-assembly of the 1:1 complex of two different amphiphiles, namely, a glucosyl-salicyl-imino conjugate (L) and phenylalanine (Phe), forming nanofibers over a period of time through pi...pi interactions. Significant enhancement observed in the fluorescence intensity of L at approximately 423 nm band and the significant decrease observed in the absorbance of the approximately 215 nm band are some characteristics of this self-assembly. Matrix-assisted laser desorption ionization/time of flight titration carried out at different time intervals supports the formation of higher aggregates. Atomic force microscopy (AFM), transmission electron microscopy, and scanning electron miscroscopy results showed the formation of nanofibers for the solutions of L with phenylalanine. In dynamic light scattering measurements, the distribution of the particles extends to a higher diameter range over time, indicating a slow kinetic process of assembly. Similar spectral and microscopy studies carried out with the control molecules support the role of the amino acid moiety over the simple -COOH moiety as well as the side chain phenyl moiety in association with the amino acid, in the formation of these fibers. All these observations support the presence of pi...pi interactions between the initially formed 1:1 complexes leading to the fiber formation. The aggregation of 1:1 complexes leading to fibers followed by the formation of bundles has been modeled by molecular mechanics studies. Thus the fiber formation with L is limited to phenylalanine and not to any other naturally occurring amino acid and hence a polymer composed of two different biocompatible amphiphiles. AFM studies carried out between the fiber forming mixture and proteins resulted in the observation that only BSA selectively adheres to the fiber among the three alpha-helical and two beta-sheet proteins studied and hence may be of use in some medical applications.

  8. Lipid peroxidation and 4-hydroxy-2-nonenal formation by copper ion bound to amyloid-beta peptide.

    PubMed

    Hayashi, Takaaki; Shishido, Naomi; Nakayama, Kenji; Nunomura, Akihiko; Smith, Mark A; Perry, George; Nakamura, Masao

    2007-12-01

    The lipid peroxidation product 4-hydroxy-2-nonenal (HNE) is proposed to be a toxic factor in the pathogenesis of Alzheimer disease. The primary products of lipid peroxidation are phospholipid hydroperoxides, and degraded reactive aldehydes, such as HNE, are considered secondary peroxidation products. In this study, we investigated the role of amyloid-beta peptide (A beta) in the formation of phospholipid hydroperoxides and HNE by copper ion bound to A beta. The A beta1-42-Cu2+ (1:1 molar ratio) complex showed an activity to form phospholipid hydroperoxides from a phospholipid, 1-palmitoyl-2-linoleoyl phosphatidylcholine, through Cu2+ reduction in the presence of ascorbic acid. The phospholipid hydroperoxides were considered to be a racemic mixture of 9-hydroperoxide and 13-hydroperoxide of the linoleoyl residue. When Cu2+ was bound to 2 molar equivalents of A beta(1-42) (2 A beta1-42-Cu2+), lipid peroxidation was inhibited. HNE was generated from one of the phospholipid hydroperoxides, 1-palmitoyl-2-(13-hydroperoxy-cis-9, trans-11-octadecadienoyl) phosphatidylcholine (PLPC-OOH), by free Cu2+ in the presence of ascorbic acid through Cu2+ reduction and degradation of PLPC-OOH. HNE generation was markedly inhibited by equimolar concentrations of A beta(1-40) (92%) and A beta(1-42) (92%). However, A beta(1-42) binding 2 or 3 molar equivalents of Cu2+ (A beta1-42-2Cu2+, A beta1-42-3Cu2+) acted as a pro-oxidant to form HNE from PLPC-OOH. These findings suggest that, at moderate concentrations of copper, A beta acts primarily as an antioxidant to prevent Cu2+-catalyzed oxidation of biomolecules, but that, in the presence of excess copper, pro-oxidant complexes of A beta with Cu2+ are formed.

  9. Crystal Structures of IAPP Amyloidogenic Segments Reveal a Novel Packing Motif of Out-of-Register Beta Sheets.

    PubMed

    Soriaga, Angela B; Sangwan, Smriti; Macdonald, Ramsay; Sawaya, Michael R; Eisenberg, David

    2016-07-07

    Structural studies of amyloidogenic segments by X-ray crystallography have revealed a novel packing motif, consisting of out-of-register β sheets, which may constitute one of the toxic species in aggregation related diseases. Here we sought to determine the presence of such a motif in islet amyloid polypeptide (IAPP), whose amyloidogenic properties are associated with type 2 diabetes. We determined four new crystal structures of segments within IAPP, all forming steric zippers. Most interestingly, one of the segments in the fibril core of IAPP forms an out-of-register steric zipper. Analysis of this structure reveals several commonalities with previously solved out-of-register fibrils. Our results provide additional evidence of out-of-register β sheets as a common structural motif in amyloid aggregates.

  10. Differential mode of interaction of ThioflavinT with native β structural motif in human α 1-acid glycoprotein and cross beta sheet of its amyloid: Biophysical and molecular docking approach

    NASA Astrophysics Data System (ADS)

    Ajmal, Mohammad Rehan; Nusrat, Saima; Alam, Parvez; Zaidi, Nida; Badr, Gamal; Mahmoud, Mohamed H.; Rajpoot, Ravi Kant; Khan, Rizwan Hasan

    2016-08-01

    The present study details the interaction mechanism of Thioflavin T (ThT) to Human α1-acid glycoprotein (AAG) applying various spectroscopic and molecular docking methods. Fluorescence quenching data revealed the binding constant in the order of 104 M-1 and the standard Gibbs free energy change value, ΔG = -6.78 kcal mol-1 for the interaction between ThT and AAG indicating process is spontaneous. There is increase in absorbance of AAG upon the interaction of ThT that may be due to ground state complex formation between ThT and AAG. ThT impelled rise in β-sheet structure in AAG as observed from far-UV CD spectra while there are minimal changes in tertiary structure of the protein. DLS results suggested the reduction in AAG molecular size, ligand entry into the central binding pocket of AAG may have persuaded the molecular compaction in AAG. Isothermal titration calorimetric (ITC) results showed the interaction process to be endothermic with the values of standard enthalpy change ΔH0 = 4.11 kcal mol-1 and entropy change TΔS0 = 10.82 kcal.mol- 1. Moreover, docking results suggested hydrophobic interactions and hydrogen bonding played the important role in the binding process of ThT with F1S and A forms of AAG. ThT fluorescence emission at 485 nm was measured for properly folded native form and for thermally induced amyloid state of AAG. ThT fluorescence with native AAG was very low, while on the other hand with amyloid induced state of the protein AAG showed a positive emission peak at 485 nm upon the excitation at 440 nm, although it binds to native state as well. These results confirmed that ThT binding alone is not responsible for enhancement of ThT fluorescence but it also required beta stacked sheet structure found in protein amyloid to give proper signature signal for amyloid. This study gives the mechanistic insight into the differential interaction of ThT with beta structures found in native state of the proteins and amyloid forms, this study reinforce

  11. Embryonic neural inducing factor churchill is not a DNA-binding zinc finger protein: solution structure reveals a solvent-exposed beta-sheet and zinc binuclear cluster.

    PubMed

    Lee, Brian M; Buck-Koehntop, Bethany A; Martinez-Yamout, Maria A; Dyson, H Jane; Wright, Peter E

    2007-08-31

    Churchill is a zinc-containing protein that is involved in neural induction during embryogenesis. At the time of its discovery, it was thought on the basis of sequence alignment to contain two zinc fingers of the C4 type. Further, binding of an N-terminal GST-Churchill fusion protein to a particular DNA sequence was demonstrated by immunoprecipitation selection assay, suggesting that Churchill may function as a transcriptional regulator by sequence-specific DNA binding. We show by NMR solution structure determination that, far from containing canonical C4 zinc fingers, the protein contains three bound zinc ions in novel coordination sites, including an unusual binuclear zinc cluster. The secondary structure of Churchill is also unusual, consisting of a highly solvent-exposed single-layer beta-sheet. Hydrogen-deuterium exchange and backbone relaxation measurements reveal that Churchill is unusually dynamic on a number of time scales, with the exception of regions surrounding the zinc coordinating sites, which serve to stabilize the otherwise unstructured N terminus and the single-layer beta-sheet. No binding of Churchill to the previously identified DNA sequence could be detected, and extensive searches using DNA sequence selection techniques could find no other DNA sequence that was bound by Churchill. Since the N-terminal amino acids of Churchill form part of the zinc-binding motif, the addition of a fusion protein at the N terminus causes loss of zinc and unfolding of Churchill. This observation most likely explains the published DNA-binding results, which would arise due to non-specific interaction of the unfolded protein in the immunoprecipitation selection assay. Since Churchill does not appear to bind DNA, we suggest that it may function in embryogenesis as a protein-interaction factor.

  12. Study of inclusion complex formation between tropaeolin OO and beta-cyclodextrin by spectrophotometry and Infrared spectroscopy.

    PubMed

    Wang, Huai You; Han, Juan; Feng, Xia Guang; Pang, Yan Ling

    2006-09-01

    The mechanism of the inclusion of tropaeolin OO (TPOO) and beta-cyclodextrin (beta-CD) has been studied by spectrophotometry. The inclusion depth of the guest molecule in the host molecule was demonstrated by infrared spectrometry. Effect of the pH, concentrations of beta-CD, solvents and ionic strength on the inclusion of TPOO and beta-CD were examined. The result showed that TPOO reacts with beta-CD to form a 1:1 host-guest complex with an apparent formation constant of 1.50 x 10(3) l mol(-1). The thermodynamic parameters of inclusion reaction, DeltaG degrees , DeltaH degrees and DeltaS degrees were obtained.

  13. Double-stranded helical twisted beta-sheet channels in crystals of gramicidin S grown in the presence of trifluoroacetic and hydrochloric acids.

    PubMed

    Llamas-Saiz, Antonio L; Grotenbreg, Gijsbert M; Overhand, Mark; van Raaij, Mark J

    2007-03-01

    Gramicidin S is a nonribosomally synthesized cyclic decapeptide antibiotic with twofold symmetry (Val-Orn-Leu-D-Phe-Pro)(2); a natural source is Bacillus brevis. Gramicidin S is active against Gram-positive and some Gram-negative bacteria. However, its haemolytic toxicity in humans limits its use as an antibiotic to certain topical applications. Synthetically obtained gramicidin S was crystallized from a solution containing water, methanol, trifluoroacetic acid and hydrochloric acid. The structure was solved and refined at 0.95 A resolution. The asymmetric unit contains 1.5 molecules of gramicidin S, two trifluoroacetic acid molecules and ten water molecules located and refined in 14 positions. One gramicidin S molecule has an exact twofold-symmetrical conformation; the other deviates from the molecular twofold symmetry. The cyclic peptide adopts an antiparallel beta-sheet secondary structure with two type II' beta-turns. These turns have the residues D-Phe and Pro at positions i + 1 and i + 2, respectively. In the crystals, the gramicidin S molecules line up into double-stranded helical channels that differ from those observed previously. The implications of the supramolecular structure for several models of gramicidin S conformation and assembly in the membrane are discussed.

  14. Efficiently engineered cell sheet using a complex of polyethylenimine–alginate nanocomposites plus bone morphogenetic protein 2 gene to promote new bone formation

    PubMed Central

    Jin, Han; Zhang, Kai; Qiao, Chunyan; Yuan, Anliang; Li, Daowei; Zhao, Liang; Shi, Ce; Xu, Xiaowei; Ni, Shilei; Zheng, Changyu; Liu, Xiaohua; Yang, Bai; Sun, Hongchen

    2014-01-01

    Regeneration of large bone defects is a common clinical problem. Recently, stem cell sheet has been an emerging strategy in bone tissue engineering. To enhance the osteogenic potential of stem cell sheet, we fabricated bone morphogenetic protein 2 (BMP-2) gene-engineered cell sheet using a complex of polyethylenimine–alginate (PEI–al) nanocomposites plus human BMP-2 complementary(c)DNA plasmid, and studied its osteogenesis in vitro and in vivo. PEI–al nanocomposites carrying BMP-2 gene could efficiently transfect bone marrow mesenchymal stem cells. The cell sheet was made by culturing the cells in medium containing vitamin C for 10 days. Assays on the cell culture showed that the genetically engineered cells released the BMP-2 for at least 14 days. The expression of osteogenesis-related gene was increased, which demonstrated that released BMP-2 could effectively induce the cell sheet osteogenic differentiation in vitro. To further test the osteogenic potential of the cell sheet in vivo, enhanced green fluorescent protein or BMP-2-producing cell sheets were treated on the cranial bone defects. The results indicated that the BMP-2-producing cell sheet group was more efficient than other groups in promoting bone formation in the defect area. Our results suggested that PEI–al nanocomposites efficiently deliver the BMP-2 gene to bone marrow mesenchymal stem cells and that BMP-2 gene-engineered cell sheet is an effective way for promoting bone regeneration. PMID:24855355

  15. Rapid Ti(III) reduction of perchlorate in the presence of beta-alanine: kinetics, pH effect, complex formation, and beta-alanine effect.

    PubMed

    Wang, Chao; Huang, Zhengdao; Lippincott, Lee; Meng, Xiaoguang

    2010-03-15

    Ti(III) reduction of perchlorate might be a useful method for the treatment of highly perchlorate-contaminated water. Though the reaction rate was usually low, we observed that beta-alanine (HOOCCH(2)CH(2)NH(2)) could significantly promote the reaction. A complete (>99.9%) perchlorate removal was obtained in a solution containing [ClO(4)(-)]=1.0mM, [Ti(III)]=40 mM, and [beta-alanine]=120 mM after 2.5h of reaction under 50 degrees C. The effects of both pH and complex formation on the reaction were then studied. The results showed that without beta-alanine the optimal pH was 2.3. When pH increased from 1.6 to 2.3, the reduction rate increased remarkably. In the pH range >2.3, however, the reduction was significantly inhibited, attributed to the formation of Ti(III) precipitate. The presence of beta-alanine at a molar ratio of [beta-alanine]:[Ti(III)]=3:1 significantly increased the reduction rate of perchlorate even at near neutral pH. This is because beta-alanine formed complexes with Ti(III), which greatly improved the total soluble [Ti(III)] in the pH range between 3.5 and 6. The findings may lead to the development of rapid treatment methods for intermittent and small stream of highly perchlorate-contaminated water, which are resulted from the manufacturing, storage, handling, use and/or disposal of large quantities of perchlorate salts.

  16. Partial purification and characterization of an enzyme involved in the formation of beta-aspartyl dipeptides in rat kidney.

    PubMed

    Tanaka, T; Hirai, M; Nakajima, T

    1978-11-01

    The formation of beta-aspartyl-glycine from asparagine and glycine was demonstrated in the supernatant of rat kidney. The enzyme involved in this process was partially purified. Based on the properties of the enzyme reaction and the coincidence of purification rates of this activity and asparaginase, it can be speculated that the enzyme is a kind of asparaginase. Examination of the preference for beta-aspartyl donors and acceptors showed that asparagine and glycine were the preferred donor and acceptor, respectively. beta-Aspartyl dipeptides also transferred their aspartyl residues to amino acids. Amino acids other than glycine also accepted the aspartyl moiety from the donors.

  17. Formation and evolution of flapping and ballooning waves in magnetospheric plasma sheet

    NASA Astrophysics Data System (ADS)

    Ma, J. Z. G.; Hirose, A.

    2016-05-01

    By adopting Lembége & Pellat's 2D plasma-sheet model, we investigate the flankward flapping motion and Sunward ballooning propagation driven by an external source (e.g., magnetic reconnection) produced initially at the sheet center. Within the ideal MHD framework, we adopt the WKB approximation to obtain the Taylor-Goldstein equation of magnetic perturbations. Fourier spectral method and Runge-Kutta method are employed in numerical simulations, respectively, under the flapping and ballooning conditions. Studies expose that the magnetic shears in the sheet are responsible for the flapping waves, while the magnetic curvature and the plasma gradient are responsible for the ballooning waves. In addition, the flapping motion has three phases in its temporal development: fast damping phase, slow recovery phase, and quasi-stabilized phase; it is also characterized by two patterns in space: propagating wave pattern and standing wave pattern. Moreover, the ballooning modes are gradually damped toward the Earth, with a wavelength in a scale size of magnetic curvature or plasma inhomogeneity, only 1-7% of the flapping one; the envelops of the ballooning waves are similar to that of the observed bursty bulk flows moving toward the Earth.

  18. Haloacetic acid and trihalomethane formation from the chlorination and bromination of aliphatic beta-dicarbonyl acid model compounds.

    PubMed

    Dickenson, Eric R V; Summers, R Scott; Croué, Jean-Philippe; Gallard, Hervé

    2008-05-01

    While it is known that resorcinol- and phenol-type aromatic structures within natural organic matter (NOM) react during drinking water chlorination to form trihalomethanes (THMs), limited studies have examined aliphatic-type structures as THM and haloacetic acid (HAA) precursors. A suite of aliphatic acid model compounds were chlorinated and brominated separately in controlled laboratory-scale batch experiments. Four and two beta-dicarbonyl acid compounds were found to be important precursors for the formation of THMs (chloroform and bromoform (71-91% mol/mol)), and dihaloacetic acids (DXAAs) (dichloroacetic acid and dibromoacetic acid (5-68% mol/mol)), respectively, after 24 h at pH 8. Based upon adsorbable organic halide formation, THMs and DXAAs, and to a lesser extent mono and trihaloacetic acids, were the majority (> 80%) of the byproducts produced for most of the aliphatic beta-dicarbonyl acid compounds. Aliphatic beta-diketone-acid-type and beta-keto-acid-type structures could be possible fast- and slow-reacting THM precursors, respectively, and aliphatic beta-keto-acid-type structures are possible slow-reacting DXAA precursors. Aliphatic beta-dicarbonyl acid moieties in natural organic matter, particularly in the hydrophilic fraction, could contribute to the significant formation of THMs and DXAAs observed after chlorination of natural waters.

  19. Formation of lobate debris aprons on Mars: Assessment of regional ice sheet collapse and debris-cover armoring

    NASA Astrophysics Data System (ADS)

    Fastook, James L.; Head, James W.; Marchant, David R.

    2014-01-01

    Lobate debris aprons (LDA) are lobate-shaped aprons surrounding scarps and isolated massifs that are concentrated in the vicinity of the northern Dichotomy Boundary on Mars. LDAs have been interpreted as (1) ice-cemented talus aprons undergoing viscous flow, (2) local debris-covered alpine-like glaciers, or (3) remnants of the collapse of a regional retreating ice sheet. We investigate the plausibility that LDAs are remnants of a more extensive regional ice sheet by modeling this process. We find that as a regional ice sheet collapses, the surface drops below cliff and massif bedrock margins, exposing bedrock and regolith, and initiating debris deposition on the surface of a cold-based glacier. Reduced sublimation due to debris-cover armoring of the proto-LDA surface produces a surface slope and consequent ice flow that carries the armoring debris away from the rock outcrops. As collapse and ice retreat continue the debris train eventually reaches the substrate surface at the front of the glacier, leaving the entire LDA armored by debris cover. Using a simplified ice flow model we are able to characterize the temperature and sublimation rate that would be necessary to produce LDAs with a wide range of specified lateral extents and thicknesses. We then apply this method to a database of documented LDA parameters (height, lateral extent) from the Dichotomy Boundary region, and assess the implications for predicted climate conditions during their formation and the range of formation times implied by the model. We find that for the population examined here, typical temperatures are in the range of -85 to -40 °C and typical sublimation rates lie in the range of 6-14 mm/a. Lobate debris apron formation times (from the point of bedrock exposure to complete debris cover) cluster near 400-500 ka. These results show that LDA length and thickness characteristics are consistent with climate conditions and a formation scenario typical of the collapse of a regional retreating

  20. Formation of High-Beta Plasma and Stable Confinement of Toroidal Electron Plasma in RT-1

    NASA Astrophysics Data System (ADS)

    Saitoh, Haruhiko

    2010-11-01

    The Ring Trap 1 (RT-1) device is a laboratory magnetosphere generated by a levitated superconducting magnet. The goals of RT-1 are to realize stable formation of ultra high-beta plasma suitable for burning advanced fusion fuels, and confinement of toroidal non-neutral plasmas including antimatter particles. RT- 1 has produced high-beta plasma in the magnetospheric configuration. The effects of coil levitation and geomagnetic field compensation [Y. Yano et al., Plasma Fusion Res. 4, 039] resulted drastic improvements of the plasma properties, and a maximum local beta value exceeded 70%. Because plasma is generated by electron cyclotron resonance heating (ECH) in the present experiment, the plasma pressure is mainly due to hot electrons, whose bremsstrahlung was observed with an x-ray CCD camera. The pressure profiles have rather steep gradient near the superconducting coil in the strong field region. The decay rates of magnetic probe and interferometer signals have different time constants, suggesting multiple temperature components. The energy confinement time estimated from the input RF power and stored magnetic energy is on the order of 1s, which is comparable to the decay time constant of the density of hot electron component. Pure electron plasma experiments are also conducted in RT-1. Radial profiles of electrostatic potential and electron density showed that the plasma rigidly rotates in the toroidal direction in the stable confinement phase. Long time confinement of toroidal non- neutral plasma for more than 300s and inward particle diffusion to strong field regions, caused by the activation of the diocotron (Kelvin-Helmholtz) instability, have been realized [Z. Yoshida et al., Phys. Rev. Lett. 104, 235004].

  1. The effect of low levels of dopants upon the formation and properties of beta-phase molybdenum nitride

    SciTech Connect

    Cairns, A.G.; Gallagher, J.G.; Hargreaves, J.S.J.; Mckay, D.; Rico, J.L.; Wilson, K.

    2010-03-15

    The addition of 1 wt% Pd, Au, Ni and Cu dopants has been demonstrated to strongly alter the morphology of beta-phase molybdenum nitride prepared by treatment of MoO{sub 3} with a 3/1 H{sub 2}/N{sub 2} mixture at 750 deg. C. Furthermore, the addition of Pd significantly enhances the surface area and the formation of the nitride phase. It is proposed that the facile formation of molybdenum bronzes in this system is important in this respect. The dopants have also been observed to modify the denitridation characteristics of the beta-phase, with an overall reduction of the proportion of NH{sub 3} formed upon using a 3/1 H{sub 2}/Ar mixture with respect to the undoped sample. - Graphical abstract: Low levels of Pd, Au, Ni and Cu dopant have significant effects upon the morphology, formation and dentitridation characteristics of beta-phase molybdenum nitride.

  2. Solvent effects on self-assembly of beta-amyloid peptide.

    PubMed Central

    Shen, C L; Murphy, R M

    1995-01-01

    beta-amyloid peptide (A beta) is the primary protein component of senile plaques in Alzheimer's disease patients. Synthetic A beta spontaneously assembles into amyloid fibrils and is neurotoxic to cortical cultures. Neurotoxicity has been associated with the degree of peptide aggregation, yet the mechanism of assembly of A beta into amyloid fibrils is poorly understood. In this work, A beta was dissolved in several different solvents commonly used in neurotoxicity assays. In pure dimethylsulfoxide (DMSO), A beta had no detectable beta-sheet content; in 0.1% trifluoroacetate, the peptide contained one-third beta-sheet; and in 35% acetonitrile/0.1% trifluoroacetate, A beta was two-thirds beta-sheet, equivalent to the fibrillar peptide in physiological buffer. Stock solutions of peptide were diluted into phosphate-buffered saline, and fibril growth was followed by static and dynamic light scattering. The growth rate was substantially faster when the peptide was predissolved in 35% acetonitrile/0.1% trifluoroacetate than in 0.1% trifluoroacetate, 10% DMSO, or 100% DMSO. Differences in growth rate were attributed to changes in the secondary structure of the peptide in the stock solvent. These results suggest that formation of an intermediate with a high beta-sheet content is a controlling step in A beta self-assembly. PMID:8527678

  3. Bone marrow stromal cell sheets may promote axonal regeneration and functional recovery with suppression of glial scar formation after spinal cord transection injury in rats.

    PubMed

    Okuda, Akinori; Horii-Hayashi, Noriko; Sasagawa, Takayo; Shimizu, Takamasa; Shigematsu, Hideki; Iwata, Eiichiro; Morimoto, Yasuhiko; Masuda, Keisuke; Koizumi, Munehisa; Akahane, Manabu; Nishi, Mayumi; Tanaka, Yasuhito

    2017-03-01

    OBJECTIVE Transplantation of bone marrow stromal cells (BMSCs) is a theoretical potential as a therapeutic strategy in the treatment of spinal cord injury (SCI). Although a scaffold is sometimes used for retaining transplanted cells in damaged tissue, it is also known to induce redundant immunoreactions during the degradation processes. In this study, the authors prepared cell sheets made of BMSCs, which are transplantable without a scaffold, and investigated their effects on axonal regeneration, glial scar formation, and functional recovery in a completely transected SCI model in rats. METHODS BMSC sheets were prepared from the bone marrow of female Fischer 344 rats using ascorbic acid and were cryopreserved until the day of transplantation. A gelatin sponge (GS), as a control, or BMSC sheet was transplanted into a 2-mm-sized defect of the spinal cord at the T-8 level. Axonal regeneration and glial scar formation were assessed 2 and 8 weeks after transplantation by immunohistochemical analyses using anti-Tuj1 and glial fibrillary acidic protein (GFAP) antibodies, respectively. Locomotor function was evaluated using the Basso, Beattie, and Bresnahan scale. RESULTS The BMSC sheets promoted axonal regeneration at 2 weeks after transplantation, but there was no significant difference in the number of Tuj1-positive axons between the sheet- and GS-transplanted groups. At 8 weeks after transplantation, Tuj1-positive axons elongated across the sheet, and their numbers were significantly greater in the sheet group than in the GS group. The areas of GFAP-positive glial scars in the sheet group were significantly reduced compared with those of the GS group at both time points. Finally, hindlimb locomotor function was ameliorated in the sheet group at 4 and 8 weeks after transplantation. CONCLUSIONS The results of the present study indicate that an ascorbic acid-induced BMSC sheet is effective in the treatment of SCI and enables autologous transplantation without requiring a

  4. Oral Administration of Thioflavin T Prevents Beta Amyloid Plaque Formation in Double Transgenic AD Mice.

    PubMed

    Sarkar, Sumit; Raymick, James; Ray, Balmiki; Lahiri, Debomoy K; Paule, Merle G; Schmued, Larry

    2015-01-01

    Alzheimer's disease (AD) is a progressive neurodegenerative disorder and the fourth leading cause of death in the United States and most common cause of adult-onset dementia. The major hallmarks of AD are the formation of senile amyloid plaques made of beta amyloid and neurofibrillary tangles (NFT) which are primarily composed of phosphorylated tau protein. Although numerous agents have been considered as providing protection against AD, identification of potential agents with neuroprotective ability is limited. Thioflavin T has been used in the past to stain amyloid beta plaques in brain. In this study, Thioflavin T (ThT) and vehicle (infant formula) were administered orally by gavage to transgenic (B6C3 APP PS1; AD-Tg) mice beginning at 4 months age and continuing until sacrifice at 9 months of age at 40 mg/kg dose. The number of amyloid plaques was reduced dramatically by ThT treatment in both male and female transgenic mice compared to those in control mice. Additionally, GFAP and Amylo-Glo labeling suggest that astrocytic hypertrophy is minimized in ThT-treated animals. Similarly, CD68 labeling, which detects activated microglia, along with Amylo-Glo labeling, suggests that microglial activation is significantly less in ThT-treated mice. Both Aβ-40 and Aβ-42 concentrations in blood rose significantly in the ThT-treated animals suggesting that ThT may inhibit the deposition, degradation, and/or clearance of Aβ plaques in brain.

  5. 5D imaging via light sheet microscopy reveals cell dynamics during the eye-antenna disc primordium formation in Drosophila

    NASA Astrophysics Data System (ADS)

    Huang, Yu Shan; Ku, Hui Yu; Tsai, Yun Chi; Chang, Chin Hao; Pao, Sih Hua; Sun, Y. Henry; Chiou, Arthur

    2017-03-01

    5D images of engrailed (en) and eye gone (eyg) gene expressions during the course of the eye-antenna disc primordium (EADP) formation of Drosophila embryos from embryonic stages 13 through 16 were recorded via light sheet microscopy and analyzed to reveal the cell dynamics involved in the development of the EADP. Detailed analysis of the time-lapsed images revealed the process of EADP formation and its invagination trajectory, which involved an inversion of the EADP anterior-posterior axis relative to the body. Furthermore, analysis of the en-expression pattern in the EADP provided strong evidence that the EADP is derived from one of the en-expressing head segments.

  6. 5D imaging via light sheet microscopy reveals cell dynamics during the eye-antenna disc primordium formation in Drosophila

    PubMed Central

    Huang, Yu Shan; Ku, Hui Yu; Tsai, Yun Chi; Chang, Chin Hao; Pao, Sih Hua; Sun, Y. Henry; Chiou, Arthur

    2017-01-01

    5D images of engrailed (en) and eye gone (eyg) gene expressions during the course of the eye-antenna disc primordium (EADP) formation of Drosophila embryos from embryonic stages 13 through 16 were recorded via light sheet microscopy and analyzed to reveal the cell dynamics involved in the development of the EADP. Detailed analysis of the time-lapsed images revealed the process of EADP formation and its invagination trajectory, which involved an inversion of the EADP anterior-posterior axis relative to the body. Furthermore, analysis of the en-expression pattern in the EADP provided strong evidence that the EADP is derived from one of the en-expressing head segments. PMID:28322328

  7. WW: An isolated three-stranded antiparallel beta-sheet domain that unfolds and refolds reversibly; evidence for a structured hydrophobic cluster in urea and GdnHCl and a disordered thermal unfolded state.

    PubMed Central

    Koepf, E. K.; Petrassi, H. M.; Sudol, M.; Kelly, J. W.

    1999-01-01

    The objective of this study was to evaluate the suitability of the WW domain as a desirable model system to understand the folding and stability of an isolated three-stranded antiparallel beta-sheet structure. The WW domain was subjected to thermal and chaotropic denaturation/reconstitution utilizing a variety of biophysical methods. This three-stranded sheet folds reversibly and cooperatively utilizing both urea and GdnHCl as denaturants; however, the denatured state retains structure in the form of a hydrophobic cluster involving at least one aromatic side chain. In contrast to chaotropic denaturation, thermal denaturation appears to be more complete and may be a two state process. The suitability of the WW domain for future studies aimed at understanding the kinetics and thermodynamics of antiparallel beta-sheet folding clearly emerges from this initial study. The most exciting and significant result in this manuscript is the finding that the chaotropic denatured state of WW has a hydrophobic cluster as discerned by near-UV CD evidence. The role that the denatured state plays in the folding and stability of a three-stranded beta-sheets, and its capacity for preventing aggregation may be particularly important and is the subject of ongoing studies. PMID:10211830

  8. Study of the {alpha}{double_prime} phase texture obtained by martensitic {beta}-{alpha}{double_prime} phase transformation induced by tensile test in a sheet of Ti5Al2Sn4Zr4Mo2Cr1Fe

    SciTech Connect

    Pionnier, D.; Humbert, M.; Philippe, M.J.; Combres, Y.

    1998-10-09

    The purpose was to investigate the texture development of the {alpha}{double_prime} orthorhombic martensite phase induced by stress within a commercial sheet of Ti5Al2Sn4Zr4Mo2Cr1Fe. First, the experimental textures of the initial b.c.c. phase, then of the b.c.c. phase and the {alpha}{double_prime} martensite phase after a uniaxial deformation were determined from pole figures. Comparison of the {alpha}{double_prime} experimental texture with a {alpha}{double_prime} texture, simulated with no variant selection from the b.c.c. texture of the initial {beta} matrix clearly shows that a strong variant selection was induced by stress. In order to better understand the formation of this {alpha}{double_prime} orthorhombic texture, texture transformations were simulated according to different variant selection assumptions. As a result, it was shown that the {alpha}{double_prime} orthorhombic texture is formed by the variants favorably oriented with respect to stresses induced during tensile test.

  9. Constraining the Late Pleistocene history of the Laurentide Ice Sheet by dating the Missinaibi Formation, Hudson Bay Lowlands, Canada

    NASA Astrophysics Data System (ADS)

    Dalton, April S.; Finkelstein, Sarah A.; Barnett, Peter J.; Forman, Steven L.

    2016-08-01

    Well-dated paleorecords from periods prior to the Last Glacial Maximum (LGM) are important for validating models of ice sheet build-up and growth. However, owing to glacial erosion, most Late Pleistocene records lie outside of the previously glaciated region, which limits their ability to inform about the dynamics of paleo-ice sheets. Here, we evaluate new and previously published chronology data from the Missinaibi Formation, a Pleistocene-aged deposit in the Hudson Bay Lowlands (HBL), Canada, located near the geographic center of the Laurentide Ice Sheet (LIS). Available radiocarbon (AMS = 44, conventional = 36), amino acid (n = 13), uranium-thorium (U-Th, n = 14), thermoluminescence (TL, n = 15) and optically stimulated luminescence (OSL, n = 5) data suggest that an ice-free HBL may have been possible during parts of Marine Isotope Stage 7 (MIS 7; ca. 243,000 to ca. 190,000 yr BP), MIS 5 (ca. 130,000 to ca. 71,000 yr BP) and MIS 3 (ca. 29,000 to ca. 57,000). While MIS 7 and MIS 5 are well-documented interglacial periods, the development of peat, forest bed and fluvial deposits dating to MIS 3 (n = 20 radiocarbon dates; 4 TL dates, 3 OSL dates), suggests that the LIS retreated and remained beyond, or somewhere within, the boundaries of the HBL during this interstadial. Ice sheet models approximate the margin of the LIS to Southern Ontario during this time, which is 700 km south of the HBL. Therefore, if correct, our data help constrain a significantly different configuration and dynamicity for the LIS than previously modelled. We can find no chronological basis to discount the MIS 3 age assignments. However, since most data originate from radiocarbon dates lying close to the reliable limit of this geochronometer, future work on dating the Missinaibi Formation using other geochronological methods (e.g. U-Th, OSL) is necessary in order to confirm the age estimates and strengthen the boundaries of the LIS during this period.

  10. Origin of life. Primordial genetics: Information transfer in a pre-RNA world based on self-replicating beta-sheet amyloid conformers.

    PubMed

    Maury, Carl Peter J

    2015-10-07

    The question of the origin of life on Earth can largely be reduced to the question of what was the first molecular replicator system that was able to replicate and evolve under the presumably very harsh conditions on the early Earth. It is unlikely that a functional RNA could have existed under such conditions and it is generally assumed that some other kind of information system preceded the RNA world. Here, I present an informational molecular system that is stable, self-replicative, environmentally responsive, and evolvable under conditions characterized by high temperatures, ultraviolet and cosmic radiation. This postulated pregenetic system is based on the amyloid fold, a functionally unique polypeptide fold characterized by a cross beta-sheet structure in which the beta strands are arranged perpendicular to the fiber axis. Beside an extraordinary structural robustness, the amyloid fold possesses a unique ability to transmit information by a three-dimensional templating mechanism. In amyloidogenesis short peptide monomers are added one by one to the growing end of the fiber. From the same monomeric subunits several structural variants of amyloid may be formed. Then, in a self-replicative mode, a specific amyloid conformer can act as a template and confer its spatially encoded information to daughter molecular entities in a repetitive way. In this process, the specific conformational information, the spatially changed organization, is transmitted; the coding element is the steric zipper structure, and recognition occurs by amino acid side chain complementarity. The amyloid information system fulfills several basic requirements of a primordial evolvable replicator system: (i) it is stable under the presumed primitive Earth conditions, (ii) the monomeric building blocks of the informational polymer can be formed from available prebiotic compounds, (iii) the system is self-assembling and self-replicative and (iv) it is adaptive to changes in the environment and

  11. Effects of Transforming Growth Factor Beta 1 in Cerebellar Development: Role in Synapse Formation

    PubMed Central

    Araujo, Ana P. B.; Diniz, Luan P.; Eller, Cristiane M.; de Matos, Beatriz G.; Martinez, Rodrigo; Gomes, Flávia C. A.

    2016-01-01

    Granule cells (GC) are the most numerous glutamatergic neurons in the cerebellar cortex and represent almost half of the neurons of the central nervous system. Despite recent advances, the mechanisms of how the glutamatergic synapses are formed in the cerebellum remain unclear. Among the TGF-β family, TGF-beta 1 (TGF-β1) has been described as a synaptogenic molecule in invertebrates and in the vertebrate peripheral nervous system. A recent paper from our group demonstrated that TGF-β1 increases the excitatory synapse formation in cortical neurons. Here, we investigated the role of TGF-β1 in glutamatergic cerebellar neurons. We showed that the expression profile of TGF-β1 and its receptor, TβRII, in the cerebellum is consistent with a role in synapse formation in vitro and in vivo. It is low in the early postnatal days (P1–P9), increases after postnatal day 12 (P12), and remains high until adulthood (P30). We also found that granule neurons express the TGF-β receptor mRNA and protein, suggesting that they may be responsive to the synaptogenic effect of TGF-β1. Treatment of granular cell cultures with TGF-β1 increased the number of glutamatergic excitatory synapses by 100%, as shown by immunocytochemistry assays for presynaptic (synaptophysin) and post-synaptic (PSD-95) proteins. This effect was dependent on TβRI activation because addition of a pharmacological inhibitor of TGF-β, SB-431542, impaired the formation of synapses between granular neurons. Together, these findings suggest that TGF-β1 has a specific key function in the cerebellum through regulation of excitatory synapse formation between granule neurons. PMID:27199658

  12. Morphological properties of tunnel valleys of the southern sector of the Laurentide Ice Sheet and implications for their formation

    NASA Astrophysics Data System (ADS)

    Livingstone, Stephen J.; Clark, Chris D.

    2016-07-01

    Tunnel valleys have been widely reported on the bed of former ice sheets and are considered an important expression of subglacial meltwater drainage. Although known to have been cut by erosive meltwater flow, the water source and development of channels has been widely debated; ranging between outburst flood events through to gradually occurring channel propagation. We have mapped and analysed the spatial pattern and morphometry of tunnel valleys and associated glacial landforms along the southern sector of the former Laurentide Ice Sheet from high-resolution digital elevation models. Around 2000 tunnel valleys have been mapped, revealing an organised pattern of sub-parallel, semi-regularly spaced valleys that form in distinctive clusters. The tunnel valleys are typically < 20 km long, and 0.5-3 km wide, although their width varies considerably down-valley. They preferentially terminate at moraines, which suggests that formation is time dependent; while we also observe some tunnel valleys that have grown headwards out of hill-hole pairs. Analysis of cross-cutting relationships between tunnel valleys, moraines and outwash fans permits reconstruction of channel development in relation to the retreating ice margin. This palaeo-drainage reconstruction demonstrates incremental growth of most valleys, with some used repeatedly or for long periods, during deglaciation, while others were abandoned shortly after their formation. Our data and interpretation support gradual (rather than a single-event) formation of most tunnel valleys with secondary contributions from flood drainage of subglacial and or supraglacially stored water down individual tunnel valleys. The distribution and morphology of tunnel valleys is shown to be sensitive to regional factors such as basal thermal regime, ice and bed topography, timing and climate.

  13. From Boron Cluster to Two-Dimensional Boron Sheet on Cu(111) Surface: Growth Mechanism and Hole Formation

    PubMed Central

    Liu, Hongsheng; Gao, Junfeng; Zhao, Jijun

    2013-01-01

    As attractive analogue of graphene, boron monolayers have been theoretically predicted. However, due to electron deficiency of boron atom, synthesizing boron monolayer is very challenging in experiments. Using first-principles calculations, we explore stability and growth mechanism of various boron sheets on Cu(111) substrate. The monotonic decrease of formation energy of boron cluster BN with increasing cluster size and low diffusion barrier for a single B atom on Cu(111) surface ensure continuous growth of two-dimensional (2D) boron cluster. During growth process, hexagonal holes can easily arise at the edge of a 2D triangular boron cluster and then diffuse entad. Hence, large-scale boron monolayer with mixed hexagonal-triangular geometry can be obtained via either depositing boron atoms directly on Cu(111) surface or soft landing of small planar BN clusters. Our theoretical predictions would stimulate further experiments of synthesizing boron sheets on metal substrates and thus enrich the variety of 2D monolayer materials. PMID:24241341

  14. Beta-carotene degradation products - formation, toxicity and prevention of toxicity.

    PubMed

    Siems, Werner; Salerno, Costantino; Crifò, Carlo; Sommerburg, Olaf; Wiswedel, Ingrid

    2009-01-01

    Carotenoids are widely used as important micronutrients in food. Furthermore, carotenoid supplementation has been used in the treatment of diseases associated with oxidative stress such as various types of cancer, inflammatory diseases or cystic fibrosis. However, in some clinical studies harmful effects have been observed, e.g. a higher incidence of lung cancer in individuals exposed to extraordinary oxidative stress. The causal mechanisms of harmful effects are still unclear. Carotenoid breakdown products (CBPs) including highly reactive aldehydes and epoxides are formed during oxidative attacks in the course of antioxidative action. We investigated the formation of CBPs by stimulated neutrophils (and at further conditions), tested the hypothesis that CBPs may exert mitochondriotoxicity and tried to prevent toxicity in the presence of members of the antioxidative network. Stimulated neutrophils are able to degrade beta-carotene and to generate a number of CBPs. Concerning mitochondriotoxicity, we found that CBPs strongly inhibit state 3 respiration of rat liver mitochondria at concentrations between 0.5 and 20 microM. This was true for retinal, beta-ionone, and for mixtures of cleavage/breakdown products. The inhibition of mitochondrial respiration was accompanied by a reduction in protein sulfhydryl content, decreasing GSH levels and redox state, and elevated accumulation of malondialdehyde. Changes in mitochondrial membrane potential favor functional deterioration in the adenine nucleotide translocator as a sensitive target. The presence of additional antioxidants such as alpha-tocopherol, ascorbic acid, N-acetyl-cysteine or others could mitigate mitochondriotoxicity. The findings reflect a basic mechanism of increasing the risk of cancer induced by carotenoid degradation products.

  15. Beta Cell Formation in vivo Through Cellular Networking, Integration and Processing (CNIP) in Wild Type Adult Mice.

    PubMed

    Doiron, Bruno; Hu, Wenchao; DeFronzo, Ralph A

    2016-01-01

    Insulin replacement therapy is essential in type 1 diabetic individuals and is required in ~40- 50% of type 2 diabetics during their lifetime. Prior attempts at beta cell regeneration have relied upon pancreatic injury to induce beta cell proliferation, dedifferentiation and activation of the embryonic pathway, or stem cell replacement. We report an alternative method to transform adult non-stem (somatic) cells into pancreatic beta cells. The Cellular Networking, Integration and Processing (CNIP) approach targets cellular mechanisms involved in pancreatic function in the organ's adult state and utilizes a synergistic mechanism that integrates three important levels of cellular regulation to induce beta cell formation: (i) glucose metabolism, (ii) membrane receptor function, and (iii) gene transcription. The aim of the present study was to induce pancreatic beta cell formation in vivo in adult animals without stem cells and without dedifferentiating cells to recapitulate the embryonic pathway as previously published (1-3). Our results employing CNIP demonstrate that: (i) insulin secreting cells can be generated in adult pancreatic tissue in vivo and circumvent the problem of generating endocrine (glucagon and somatostatin) cells that exert deleterious effects on glucose homeostasis, and (ii) longterm normalization of glucose tolerance and insulin secretion can be achieved in a wild type diabetic mouse model. The CNIP cocktail has the potential to be used as a preventative or therapeutic treatment or cure for both type 1 and type 2 diabetes.

  16. β-sheet-like formation during the mechanical unfolding of prion protein

    NASA Astrophysics Data System (ADS)

    Tao, Weiwei; Yoon, Gwonchan; Cao, Penghui; Eom, Kilho; Park, Harold S.

    2015-09-01

    Single molecule experiments and simulations have been widely used to characterize the unfolding and folding pathways of different proteins. However, with few exceptions, these tools have not been applied to study prion protein, PrPC, whose misfolded form PrPSc can induce a group of fatal neurodegenerative diseases. Here, we apply novel atomistic modeling based on potential energy surface exploration to study the constant force unfolding of human PrP at time scales inaccessible with standard molecular dynamics. We demonstrate for forces around 100 pN, prion forms a stable, three-stranded β-sheet-like intermediate configuration containing residues 155-214 with a lifetime exceeding hundreds of nanoseconds. A mutant without the disulfide bridge shows lower stability during the unfolding process but still forms the three-stranded structure. The simulations thus not only show the atomistic details of the mechanically induced structural conversion from the native α-helical structure to the β-rich-like form but also lend support to the structural theory that there is a core of the recombinant PrP amyloid, a misfolded form reported to induce transmissible disease, mapping to C-terminal residues ≈160-220.

  17. β-sheet-like formation during the mechanical unfolding of prion protein

    SciTech Connect

    Tao, Weiwei; Cao, Penghui; Park, Harold S.; Yoon, Gwonchan; Eom, Kilho

    2015-09-28

    Single molecule experiments and simulations have been widely used to characterize the unfolding and folding pathways of different proteins. However, with few exceptions, these tools have not been applied to study prion protein, PrP{sup C}, whose misfolded form PrP{sup Sc} can induce a group of fatal neurodegenerative diseases. Here, we apply novel atomistic modeling based on potential energy surface exploration to study the constant force unfolding of human PrP at time scales inaccessible with standard molecular dynamics. We demonstrate for forces around 100 pN, prion forms a stable, three-stranded β-sheet-like intermediate configuration containing residues 155-214 with a lifetime exceeding hundreds of nanoseconds. A mutant without the disulfide bridge shows lower stability during the unfolding process but still forms the three-stranded structure. The simulations thus not only show the atomistic details of the mechanically induced structural conversion from the native α-helical structure to the β-rich-like form but also lend support to the structural theory that there is a core of the recombinant PrP amyloid, a misfolded form reported to induce transmissible disease, mapping to C-terminal residues ≈160-220.

  18. Reduction of Liquid Clad Formation Due to Solid State Diffusion in Clad Brazing Sheet

    NASA Astrophysics Data System (ADS)

    Benoit, Michael J.; Whitney, Mark A.; Wells, Mary A.; Winkler, Sooky

    2016-12-01

    Warm forming operations have shown promise in expanding automotive heat exchanger designs by increasing forming limits of clad brazing sheet. The impact of isothermal holds below the clad melting temperature on subsequent brazeability has not previously been studied in detail. The effect of these holds on brazeability, as measured by the clad thickness loss due to solid state diffusion of Si out of the clad layer prior to clad melting, was assessed through parallel DSC and optical microscopy measurements, as well as through the use of a previously developed model. EPMA measurements were also performed to support the other measures. Overall, the same trends were predicted by DSC, microscopy, and the theoretical model; however, the DSC predictions were unable to accurately predict remaining clad thickness prior to melting, even after correcting the data for clad-core interactions. Microscopy measurements showed very good agreement with the model predictions, although there were slight discrepancies at short hold times due to the inability of the model to account for clad loss during heating to the brazing temperature. Further microscopy measurements showed that when the heating rate is set below a critical value, there is a reduction in the clad thickness from the as-received condition.

  19. On the formation of the tunnel valleys of the southern Laurentide ice sheet

    USGS Publications Warehouse

    Hooke, R. LeB; Jennings, C.E.

    2006-01-01

    Catastrophic releases of meltwater, produced by basal melting and stored for decades in subglacial reservoirs at high pressure, may have been responsible for eroding the broad, deep tunnel valleys that are common along the margins of some lobes of the southern Laurentide ice sheet. We surmise that these releases began when the high water pressure was transmitted to the margin through the substrate. The water pressure in the substrate at the margin would then have been significantly above the overburden pressure, leading to sapping failure. Headward erosion of a conduit in the substrate (piping) could then tap the stored water, resulting in the outburst. In some situations, development of a siphon may have lowered the reservoir below its overflow level, thus tapping additional water. Following the flood, the seal could have reformed and the reservoir refilled, setting up conditions for another outburst. Order of magnitude calculations suggest that once emptied, a subglacial reservoir could refill in a matter of decades. The amount of water released during several outbursts appears to be sufficient to erode a tunnel valley. We think that tunnel valleys are most likely to have formed in this way where and when the glacier margin was frozen to the bed and permafrost extended from the glacier forefield several kilometers back under the glacier, as reservoirs would then have been larger and more common, and the seal more robust and more likely to reform after an outburst. ?? 2006 Elsevier Ltd. All rights reserved.

  20. Formation of carbon nanoscrolls from graphene sheet: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Zhang, Danhui; Yang, Houbo

    2016-12-01

    In recent year, carbon nanoscrolls have attracted intensive attention both in theory and experiments for their unique and excellent fundamental properties and the wide range of potential applications. In this paper, the fabrication of carbon nanoscrolls using graphene and carbon nanotubes has been studied by molecular dynamics (MD) method. The formation mechanism of carbon nanoscrolls has been presented convincing explanations. Furthermore, the position and number of carbon nanotubes also influence the formation of carbon nanoscrolls. Our theoretical results will provide researchers a powerful guide and helpful assistance in designing better targeted programs in experiments.

  1. Spontaneous association of hydrophobized dextran and poly-beta-cyclodextrin into nanoassemblies. Formation and interaction with a hydrophobic drug.

    PubMed

    Daoud-Mahammed, S; Ringard-Lefebvre, C; Razzouq, N; Rosilio, V; Gillet, B; Couvreur, P; Amiel, C; Gref, R

    2007-03-01

    New nanoassemblies were instantaneously prepared by mixing two aqueous solutions, one containing a beta-cyclodextrin polymer (pbetaCD), and the other a hydrophobically modified by alkyl chains dextran (MD). The formation mechanism and the inner structure of these nanoassemblies were analysed using surface tension measurements and (1)H NMR spectroscopy. The effect of a hydrophobic guest molecule, such as benzophenone (BZ), on the formation and stability of the nanoassemblies was also evaluated. MD exhibited the typical behaviour of a soluble amphiphilic molecule and adsorbed at the air/water interface. Whereas the injection of native beta-CDs in the solution beneath the adsorbed MD monolayer did not produce any change in the surface tension, that of the pbetaCD resulted in an increase in the surface tension, indicating the desorption of the polymer from the interface. This result accounts for a cooperative effect of beta-CDs linked together in the pbetaCD polymer on dextran desorption. The presence of benzophenone in the system hindered the sequestration of dextran alkyl moieties by beta-CD in the polymer without impeding the formation of associative nanoassemblies of 100-200 nm. (1)H NMR investigations demonstrated that, in the BZ-loaded nanoassemblies, the hydrophobic molecule was mainly located into the cyclodextrin cavities.

  2. Mice deficient in 11beta-hydroxysteroid dehydrogenase type 1 lack bone marrow adipocytes, but maintain normal bone formation.

    PubMed

    Justesen, Jeannette; Mosekilde, Lis; Holmes, Megan; Stenderup, Karin; Gasser, Jürg; Mullins, John J; Seckl, Jonathan R; Kassem, Moustapha

    2004-04-01

    Glucocorticoids (GCs) exert potent, but poorly characterized, effects on the skeleton. The cellular activity of GCs is regulated at a prereceptor level by 11beta-hydroxysteroid dehydrogenases (11betaHSDs). The type 1 isoform, which predominates in bone, functions as a reductase in intact cells and regenerates active cortisol (corticosterone) from circulating inert 11-keto forms. The aim of the present study was to investigate the role of this intracrine activation of GCs on normal bone physiology in vivo using mice deficient in 11betaHSD1 (HSD1(-/-)). The HSD1(-/-) mice exhibited no significant changes in cortical or trabecular bone mass compared with wild-type (Wt) mice. Aged HSD1(-/-) mice showed age-related bone loss similar to that observed in Wt mice. Histomorphometric analysis showed similar bone formation and bone resorption parameters in HSD1(-/-) and Wt mice. However, examination of bone marrow composition revealed a total absence of marrow adipocytes in HSD1(-/-) mice. Cells from Wt and HSD1(-/-) mice exhibited similar growth rates as well as similar levels of production of osteoblastic markers. The adipocyte-forming capacity of in vitro cultured bone marrow stromal cells and trabecular osteoblasts was similar in HSD1(-/-) and Wt mice. In conclusion, our results suggest that 11betaHSD1 amplification of intracellular GC actions in mice may be required for bone marrow adipocyte formation, but not for bone formation. The clinical relevance of this observation remains to be determined.

  3. The geologic mapping of Venus using C-1 format: Sheets 75N254, 60N263

    NASA Technical Reports Server (NTRS)

    Shalimov, I. V.

    1992-01-01

    The results of geologic mapping of Venus, produced on the base of Magellan images, are presented. We submit two C-1 format geologic maps with the appropriate legend. The mapping territory was taken from Venera 15 and 16 missions and geologic maps were composed. Magellan images allow us to divide some types of the plains units to determine the lava flow direction and to map with better accuracy.

  4. Unfolding Simulations of Holomyoglobin from Four Mammals: Identification of Intermediates and β-Sheet Formation from Partially Unfolded States

    PubMed Central

    Dasmeh, Pouria; Kepp, Kasper P.

    2013-01-01

    Myoglobin (Mb) is a centrally important, widely studied mammalian protein. While much work has investigated multi-step unfolding of apoMb using acid or denaturant, holomyoglobin unfolding is poorly understood despite its biological relevance. We present here the first systematic unfolding simulations of holoMb and the first comparative study of unfolding of protein orthologs from different species (sperm whale, pig, horse, and harbor seal). We also provide new interpretations of experimental mean molecular ellipticities of myoglobin intermediates, notably correcting for random coil and number of helices in intermediates. The simulated holoproteins at 310 K displayed structures and dynamics in agreement with crystal structures (Rg ∼1.48–1.51 nm, helicity ∼75%). At 400 K, heme was not lost, but some helix loss was observed in pig and horse, suggesting that these helices are less stable in terrestrial species. At 500 K, heme was lost within 1.0–3.7 ns. All four proteins displayed exponentially decaying helix structure within 20 ns. The C- and F-helices were lost quickly in all cases. Heme delayed helix loss, and sperm whale myoglobin exhibited highest retention of heme and D/E helices. Persistence of conformation (RMSD), secondary structure, and ellipticity between 2–11 ns was interpreted as intermediates of holoMb unfolding in all four species. The intermediates resemble those of apoMb notably in A and H helices, but differ substantially in the D-, E- and F-helices, which interact with heme. The identified mechanisms cast light on the role of metal/cofactor in poorly understood holoMb unfolding. We also observed β-sheet formation of several myoglobins at 500 K as seen experimentally, occurring after disruption of helices to a partially unfolded, globally disordered state; heme reduced this tendency and sperm-whale did not display any sheet propensity during the simulations. PMID:24386077

  5. Regulation of cyclic AMP formation in cultures of human foetal astrocytes by beta 2-adrenergic and adenosine receptors.

    PubMed

    Woods, M D; Freshney, R I; Ball, S G; Vaughan, P F

    1989-09-01

    Two cell cultures, NEP2 and NEM2, isolated from human foetal brain have been maintained through several passages and found to express some properties of astrocytes. Both cell cultures contain adenylate cyclase stimulated by catecholamines with a potency order of isoprenaline greater than adrenaline greater than salbutamol much greater than noradrenaline, which is consistent with the presence of beta 2-adrenergic receptors. This study reports that the beta 2-adrenergic-selective antagonist ICI 118,551 is approximately 1,000 times more potent at inhibiting isoprenaline stimulation of cyclic AMP (cAMP) formation in both NEP2 and NEM2 than the beta 1-adrenergic-selective antagonist practolol. This observation confirms the presence of beta 2-adrenergic receptors in these cell cultures. The formation of cAMP in NEP2 is also stimulated by 5'-(N-ethylcarboxamido)adenosine (NECA) more potently than by either adenosine or N6-(L-phenylisopropyl)adenosine (L-PIA), which suggests that this foetal astrocyte expresses adenosine A2 receptors. Furthermore, L-PIA and NECA inhibit isoprenaline stimulation of cAMP formation, a result suggesting the presence of adenosine A1 receptors on NEP2. The presence of A1 receptors is confirmed by the observation that the A1-selective antagonist 8-cyclopentyl-1,3-dipropylxanthine reverses the inhibition of isoprenaline stimulation of cAMP formation by L-PIA and NECA. Additional evidence that NEP2 expresses adenosine receptors linked to the adenylate cyclase-inhibitory GTP-binding protein is provided by the finding that pretreatment of these cells with pertussis toxin reverses the adenosine inhibition of cAMP formation stimulated by either isoprenaline or forskolin.

  6. Formation and bioactivity of porous and nanostructured TiO2/beta-TCP coating on titanium.

    PubMed

    Hu, Hongjie; Liu, Xuanyong; Meng, Fanhao; Ding, Chuanxian

    2011-12-01

    Titanium and its alloys have been widely used as hard tissue implants due to their excellent mechanical properties and biocompatibility. However, their near bio-inertness and metallic ion release are still the problems with clinical uses. In this paper, porous and nanostructured TiO2/beta-tricalcium phosphate (beta-TCP) composite coatings were prepared on titanium substrates by plasma electrolytic oxidation (PEO) in a Ca and P-containing electrolyte. The influence of PEO electric current density on phase composition and bioactivity of the coatings were studied. X-ray diffraction, scanning electron microscopy and Fourier transfer infrared spectroscopy were utilized to characterize the phase composition and microstructure of the coatings. Simulated body fluid immersion tests were employed on the coatings to evaluate their bioactivity. The results reveal that TiO2/beta-TCP composite coating with pores size less than 10 microm and grains of 50-100 nm in size was prepared. The electric current density of PEO is an important factor in the formation of the composite coating. The TiO2/beta-TCP composite coating shows good bioactivity, which are attributed to the incorporation of beta-TCP.

  7. The role of proline-containing peptide triads in β-sheet formation: A kinetic study.

    PubMed

    Takor, Gaius A; Higashiya, Seiichiro; Sikirzhytski, Vitali K; Seeley, Jason P; Lednev, Igor K; Welch, John T

    2015-06-01

    The design of biomimetic materials through molecular self-assembly is a growing area of modern nanotechnology. With problems of protein folding, self-assembly, and sequence-structure relationships as essential in nanotechnology as in biology, the effect of the nucleation of β-hairpin formation by proline on the folding process has been investigated in model studies. Previously such studies were limited to investigations of the influence of proline on the formation of turns in short peptide sequences. The effect of proline-based triads on the folding of an 11-kDa amyloidogenic peptide GH6[(GA)3GY(GA)3GE]8 GAH6 (YE8) was investigated by selective substitution of the proline-substituted triads at the γ-turn sites. The folding and fibrillation of the singly proline-substituted polypeptides, e.g., GH6-[(GA)3GY(GA)3GE]7(GA)3GY(GA)3PD-GAH6 (8PD), and doubly proline-substituted polypeptides, e.g., GH6-[(GA)3GY(GA)3GE]3(GA)3GY(GA)3PD[(GA)3GY(GA)3GE]3(GA)3GY(GA)3PD-GAH6 (4,8PD), were directly monitored by circular dichroism and deep UV resonance Raman and fluorescence spectroscopies. These findings were used to identify the essential folding domains, i.e., the minimum number of β-strands necessary for stable folding. These experimental findings may be especially useful in the design and construction of peptidic materials for a wide range of applications as well as in understanding the mechanisms of folding critical to fibril formation.

  8. Folding and aggregation of TEM beta-lactamase: analogies with the formation of inclusion bodies in Escherichia coli.

    PubMed Central

    Georgiou, G.; Valax, P.; Ostermeier, M.; Horowitz, P. M.

    1994-01-01

    The enzyme TEM beta-lactamase has been used as a model for understanding the pathway leading to formation of inclusion bodies in Escherichia coli. The equilibrium denaturation of TEM beta-lactamase revealed that an intermediate that has lost enzymatic activity, native protein fluorescence, and UV absorption, but retains 60% of the native circular dichroism signal, becomes populated at intermediate (1.0-1.4 M) concentrations of guanidium chloride (GdmCl). This species exhibits a large increase in bis-1-anilino-8-naphthalene sulfonic acid fluorescence, indicating the presence of exposed hydrophobic surfaces. When TEM beta-lactamase was unfolded in different initial concentrations of GdmCl and refolded to the same final conditions by dialysis a distinct minimum in the yield of active protein was observed for initial concentrations of GdmCl in the 1.0-1.5 M range. It was shown that the lower reactivation yield was solely due to the formation of noncovalently linked aggregates. We propose that the aggregation of TEM beta-lactamase involves the association of a compact state having partially exposed hydrophobic surfaces. This hypothesis is consistent with our recent findings that TEM beta-lactamase inclusion bodies contains extensive secondary structure (Przybycien TM, Dunn JP, Valax P, Georgiou G, 1994, Protein Eng 7:131-136). Finally, we have also shown that protein aggregation was enhanced at higher temperatures and in the presence of 5 mM dithiothreitol and was inhibited by the addition of sucrose. These conditions exert a similar effect on the formation of inclusion bodies in vivo. PMID:7703842

  9. Formation of adherens and communicating junctions coordinate the differentiation of the shedding-layer and beta-epidermal generation in regenerating lizard epidermis.

    PubMed

    Alibardi, Lorenzo

    2014-06-01

    In the lizard epidermis, the formation of a stratified alpha- and beta-layer, separated by a shedding complex for molting, suggests that keratinocytes communicate in a coordinated manner after they leave the basal layers during the shedding cycle. I have therefore studied the localization of cell junctional proteins such as beta-catenin and connexins 43 and 26 during scale regeneration in lizard using immunocytochemistry. Beta-catenin is also detected in nuclei of basal cells destined to give rise to the Oberhäutchen and beta-cells suggesting activation of the Wnt-pathway during beta-cell differentiation. The observations show that cells of the entire shedding layer (clear and Oberhäutchen) and beta-layer are connected by beta-catenin (adherens junctions) and connexins (communicating junctions) during their differentiation. This likely cell coupling determines the formation of a distinct shedding and beta-layer within the regenerating epidermis. The observed pattern of cell junctional stratification suggests that after departing from the basal layer Oberhäutchen and beta-cells form a continuous communicating compartment that coordinates the contemporaneous differentiation along the entire scale. While the beta-layer matures the junctions are lost while other cell junctions are formed in the following mesos- and alpha-cell layers. This process determines the formation of layers with different texture (harder or softer) and the precise localization of the shedding layer within lizard epidermis.

  10. Altered beta-adrenergic receptor-stimulated cAMP formation in cultured skin fibroblasts from Alzheimer donors.

    PubMed

    Huang, H M; Gibson, G E

    1993-07-15

    An alteration in signal transduction systems in Alzheimer's disease would likely be of pathophysiological significance, because these steps are critical to normal brain function. Since dynamic processes are difficult to study in autopsied brain, the current studies utilized cultured skin fibroblasts. The beta-adrenergic-stimulated increase in cAMP was reduced approximately 80% in fibroblasts from Alzheimer's disease compared with age-matched controls. The deficit in Alzheimer fibroblasts in response to various adrenergic agonists paralleled their beta-adrenergic potency, and enhancement of cAMP accumulation by a non-adrenergic agonist, such as prostaglandin E1, was similar in Alzheimer and control fibroblasts. Diminished adenylate cyclase activity did not underlie these abnormalities, since direct stimulation of adenylate cyclase by forskolin elevated cAMP production equally in Alzheimer and control fibroblasts. Cholera toxin equally stimulated cAMP formation in Alzheimer and control fibroblasts. Moreover, cholera toxin partially reduced isoproterenol-induced cAMP deficit in Alzheimer fibroblasts. Pertussis toxin, on the other hand, did not alter the Alzheimer deficits. The results suggest either that the coupling of the GTP-binding protein(s) to the beta-adrenergic receptor is abnormal or that the sensitivity of receptor is altered with Alzheimer's disease. Further, any hypothesis about Alzheimer's disease must explain why a reduced beta-adrenergic-stimulated cAMP formation persists in tissue culture.

  11. Cementum- and periodontal ligament-like tissue formation by dental follicle cell sheets co-cultured with Hertwig's epithelial root sheath cells.

    PubMed

    Bai, Yudi; Bai, Yuxiang; Matsuzaka, Kenichi; Hashimoto, Sadamitsu; Fukuyama, Tatsuro; Wu, Lian; Miwa, Tsuneyuki; Liu, Xiaohui; Wang, Xiaojing; Inoue, Takashi

    2011-06-01

    Dental follicle cells (DFCs) are believed contain the precursor cells of the periodontium and can form cell sheets by secreting extracellular matrix (ECM) proteins. Cell sheet engineering has been recently developed and applied successfully in the field of tissue regeneration. However, research on the in vitro characteristics of DFC sheets is lacking and an assessment of whether DFC sheets can produce periodontal tissues in vivo has not been reported. To test the characteristics and applicability of DFC sheets in this field, we established a co-culture system of rat DFCs and Hertwig's epithelial root sheath (HERS) cells in vitro, and included the following controls: a co-culture of DFCs and alveolar mucosa epithelial cells, DFCs with no cells in the upper chamber, and DFCs cultured without an upper chamber. After 3 weeks of co-culturing the cells, the DFC sheets were transplanted into adult male rats' omenta. One week after co-culturing DFCs with HERS cells, mRNA levels of collagen type I (COL-1), alkaline phosphatase (ALP), runt related transcription factor 2 (Runx 2) and bone sialoprotein (BSP) were increased significantly. In addition, after 3 weeks of co-culturing the cells, the numbers of ALP-, osteocalcin (OCN)-, BSP- and osteoprotegerin (OPG)-positive DFCs increased. The DFCs also produced more calcified nodules and exhibited an increased number of subcellular organelles, which are important for protein synthesis and secretion. Moreover, gap junctions were found between the experimental DFCs within the sheet. Five weeks of in vivo growth of DFC sheets pre-exposed to HERS cells led to the formation of cementum-like tissues, which were positive for OCN, BSP and OPG, as well as the formation of periodontal ligament-like tissues, which were positive for COL-1. In contrast, control cells only produced fibrous tissues. These results indicate that the DFC sheets induced by HERS cells are able to produce periodontal tissues through epithelial

  12. Non-linear Tearing and Flux rope Formation in 3D Null Current Sheets

    NASA Astrophysics Data System (ADS)

    Wyper, P. F.; Pontin, D. I.

    2014-12-01

    The manner in which small scale structure affects the large scale reconnection process in realistic 3D geometries is still an unsolved problem. With the increase in computational resources and improvements in satellite instrumentation, signatures of flux ropes or "plasmoids" are now observed with increasing regularity, yet their formation and dynamics are poorly understood. It has been demonstrated that even at MHD scales, in 2D rapid non-linear tearing of Sweet-Parker-like layers forms multiple magnetic islands ("plasmoids") and allows the reconnection rate to become almost independent of the Lundquist number (the "plasmoid instability"). This work presents some of our recent theoretical work focussing on an analogous instability in a fully 3D geometry. Using results from a series of 3D high resolution MHD simulations, the formation and evolution of fully three dimensional "flux rope" structures following the 3D plasmoid instability will be presented, and their effects on the manner of the reconnection process as a whole discussed.

  13. An endosomal beta COP is involved in the pH-dependent formation of transport vesicles destined for late endosomes

    PubMed Central

    1996-01-01

    In this paper, we show that beta COP is present on endosomes and is required for the formation of vesicles which mediate transport from early to late endosomes. Both the association of beta COP to endosomal membranes as well as transport vesicle formation depend on the lumenal pH. We find that epsilon COP, but not gamma COP, is also associated to endosomes, and that this association is also lumenal pH dependent. Our data, thus, indicate that a subset of COPs is part of the mechanism regulating endosomal membrane transport, and that membrane association of these COPs is controlled by the acidic properties of early endosomes, presumably via a trans-membrane pH sensor. PMID:8601610

  14. Beta4 integrin-dependent formation of polarized three-dimensionalarchitecture confers resistance to apoptosis in normal and malignantmammary epithelium

    SciTech Connect

    Weaver, Valerie M.; Lelievre, Sophie; Lakins, Johnathon N.; Chrenek, Micah A.; Jones, Jonathan C.R.; Giancotti, Filippo; Werb, Zena; Bissell, Mina J.

    2002-08-27

    Tumor cells can evade chemotherapy by acquiring resistanceto apoptosis. We investigated the molecular mechanism whereby malignantand nonmalignant mammary epithelial cells become insensitive toapoptosis. We show that regardless of growth status formation ofpolarized, three-dimensional structures driven by basement membraneconfers protection to apoptosis in both nonmalignant and malignantmammary epithelial cells. By contrast, irrespective of their malignantstatus, nonpolarized structures are sensitive to induction of apoptosis.Resistance to apoptosis requires ligation of beta4 integrins, whichregulates tissue polarity, hemidesmosome formation and NFkB activation.Expression of beta4 integrin that lacks the hemidesmosome targetingdomain interferes with tissue polarity and NFkB activation and permitsapoptosis. These results indicate that integrin-induced polarity maydrive tumor cell resistance to apoptosis-inducing agents via effects onNFkB.

  15. Thymosin Beta4 Regulates Cardiac Valve Formation Via Endothelial-Mesenchymal Transformation in Zebrafish Embryos

    PubMed Central

    Shin, Sun-Hye; Lee, Sangkyu; Bae, Jong-Sup; Jee, Jun-Goo; Cha, Hee-Jae; Lee, You Mie

    2014-01-01

    Thymosin beta4 (TB4) has multiple functions in cellular response in processes as diverse as embryonic organ development and the pathogeneses of disease, especially those associated with cardiac coronary vessels. However, the specific roles played by TB4 during heart valve development in vertebrates are largely unknown. Here, we identified a novel function of TB4 in endothelialmesenchymal transformation (EMT) in cardiac valve endocardial cushions in zebrafish. The expressions of thymosin family members in developing zebrafish embryos were determined by whole mount in situ hybridization. Of the thymosin family members only zTB4 was expressed in the developing heart region. Cardiac valve development at 48 h post fertilization was defected in zebrafish TB4 (zTB4) morpholino-injected embryos (morphants). In zTB4 morphants, abnormal linear heart tube development was observed. The expressions of bone morphogenetic protein (BMP) 4, notch1b, and hyaluronic acid synthase (HAS) 2 genes were also markedly reduced in atrio-ventricular canal (AVC). Endocardial cells in the AVC region were stained with anti-Zn5 antibody reactive against Dm-grasp (an EMT marker) to observe EMT in developing cardiac valves in zTB4 morphants. EMT marker expression in valve endothelial cells was confirmed after transfection with TB4 siRNA in the presence of transforming growth factor β (TGFβ) by RT-PCR and immunofluorescent assay. Zn5-positive endocardial AVC cells were not observed in zTB4 morphants, and knockdown of TB4 suppressed TGF-β-induced EMT in ovine valve endothelial cells. Taken together, our results demonstrate that TB4 plays a pivotal role in cardiac valve formation by increasing EMT. PMID:24732964

  16. Lactate adversely affects the in vitro formation of endothelial cell tubular structures through the action of TGF-{beta}1

    SciTech Connect

    Schmid, Stephan A. . E-mail: leoni.kunz-schughart@oncoray.de; Gaumann, Andreas; Wondrak, Marit; Eckermann, Christoph; Schulte, Stephanie; Mueller-Klieser, Wolfgang; Wheatley, Denys N.; Kunz-Schughart, Leoni A.

    2007-07-15

    When lactate accumulation in a tumor microenvironment reaches an average concentration of 10-20 mM, it tends to reflect a high degree of malignancy. However, the hypothesis that tumor-derived lactate has a number of partially adverse biological effects on malignant and tumor-associated host cells requires further evidence. The present study attempted to evaluate the impact of lactate on the process of angiogenesis, in particular on the formation of tubular structures. The endothelial cell (EC) network in desmoplastic breast tumors is primarily located in areas of reactive fibroblastic stroma. We employed a fibroblast-endothelial cell co-culture model as in vitro angiogenesis system normally producing florid in vitro tubule formation to analyze this situation. In contrast to previous studies, we found that lactate significantly reduces EC network formation in a dose-dependent manner as quantified by semi-automated morphometric analyses following immunohistochemical staining. The decrease in CD31-positive tubular structures and the number of intersections was independent of VEGF supplementation and became more pronounced in the presence of protons. The number of cells, primarily of the fibroblast population, was reduced but cell loss could not be attributed to a decrease in proliferative activity or pronounced apoptotic cell death. Treatment with 10 mM lactate was accompanied by enhanced mRNA expression and release of TGF-{beta}1, which also shows anti-angiogenic activity in the model. Both TGF-{beta}1 and lactate induced myofibroblastic differentiation adjacent to the EC tubular structures. The lactate response on the EC network was diminished by TGF-{beta}1 neutralization, indicating a causal relationship between lactate and TGF-{beta}1 in the finely tuned processes of vessel formation and maturation which may also occur in vivo within tumor tissue.

  17. Formation of beta-fructosyl compounds of pyridoxine in growing culture of Aspergillus niger.

    PubMed

    Suzuki, Y; Uchida, K

    1993-06-01

    Two pyridoxine compounds were found to be formed in a culture filtrate of Aspergillus niger and A. sydowi, when grown in a medium containing sucrose and pyridoxine. Each of the two compounds I and II was obtained as a white powdered preparation by preparative paper chromatography, gel filtration on Toyopearl HW-40S and Sephadex G-10 columns, DEAE-cellulose column chromatography, and lyophilization. Compounds I and II were identified as 5'-O-(beta-D-fructofuranosyl)-pyridoxine and 5'-O-[beta-D-fructofuranosyl-(2-->1)-beta-D-fructofuranosyl]-pyridoxine, on the basis of the various experimental results, viz., elementary analyses, UV, 1H-, and 13C-NMR spectra, products by hydrolysis with acid and yeast beta-D-fructofuranosidase, migration on paper electrophoresis, and Gibbs reaction in the presence and absence of boric acid. Levansucrase from Microbacterium laevaniformans and yeast beta-D-fructofuranosidase did not catalyze the beta-D-fructofuranosyl transfer from sucrose to pyridoxine to give rise to beta-D-fructofuranosyl-pyridoxine.

  18. [Simulation of alpha-helix and beta-hairpin formation in water-soluble proteins by the code physics method].

    PubMed

    Shestopalov, B V

    2007-01-01

    One of the possible ways for complete and final solution of the problem of determination of three-dimensional structure of proteins on amino acid sequence is simulation of protein three-dimensional structure formation. The use of the code physics method developed by the author has been suggested to fulfill this task. The simulation of alpha-helix and beta-hairpin formation in water-soluble proteins as a start of realization of the plan is described here. The results of the simulation were compared with the experimental data for 14 proteins of no more than 50 amino acids and therefore with little number of alpha-helices and beta-strands (to meet limits of simulation process) and with secondary structure predictions by the best to data methods of protein secondary structure prediction, PSIpred, PORTER and PROFsec. Secondary structure of the proteins, obtained as a result of the simulation of alpha-helix and beta-hairpin formation using the code physics method, corresponded completely to experimental data while the secondary structure predicted by the PSIpred, PORTER and PROFsec methods differed from these data significantly.

  19. Lipid-specific β-sheet formation in a mussel byssus protein domain.

    PubMed

    Heim, Markus; Elsner, Martina B; Scheibel, Thomas

    2013-09-09

    Intrinsically disordered proteins (IDP) or regions (IDR) can adopt multiple conformational states, depending on the interaction partners they encounter. This enables proteins or individual domains to fulfill multiple functions. Here, we analyzed the flank sequences of preCol-NG, one of three collagenous proteins of a mussel byssus thread governing its mechanical performance. preCol-NG comprises a collagen domain and nonrepetitive termini enclosing specific flank regions characterized by tandem repeats known from silk proteins, protein elastomers, and plant cell wall-associated proteins. We recombinantly produced a protein mimicking the M. galloprovincialis preCol-NG C-terminal flank region. The protein was intrinsically unfolded in solution, even at elevated temperatures. However, upon contact with small unilamellar vesicles (SUVs) reversible β-structure formation occurred, reminiscent of partitioning-folding coupling. This behavior of preCol-NG flank domains likely impacts byssogenesis and sheds new light on a distinct mechanism of how fibrous protein materials might be achieved by lipid-induced self-assembly in nature.

  20. Supraglacial Lakes in the Percolation Zone of the Western Greenland Ice Sheet: Formation and Development using Operation IceBridge Snow Radar and ATM (2009-2014)

    NASA Astrophysics Data System (ADS)

    Chen, C.; Howat, I. M.; de la Peña, S.

    2015-12-01

    Surface meltwater lakes on the Greenland Ice Sheet have appeared at higher elevations, extending well into the percolation zone, under recent warming, with the largest expansion occurring in the western Greenland Ice Sheet. The conditions that allow lakes to form atop firn are poorly constrained, but the formation of new lakes imply changes in the permeability of the firn at high elevations, promoting meltwater runoff. We explore the formation and evolution of new surface lakes in this region above 1500 meters, using a combination of satellite imagery and repeat Snow (2-6.5 GHz) radar echograms and LIDAR measurements from NASA's Operation IceBridge of 2009-2014. We identify conditions for surface lake formation at their farthest inland extent and suggest behaviors of persistence and lake drainage are due to differences in regional ice dynamics.

  1. Driving Cartilage Formation in High-Density Human Adipose-Derived Stem Cell Aggregate and Sheet Constructs Without Exogenous Growth Factor Delivery

    PubMed Central

    Dang, Phuong N.; Solorio, Loran D.

    2014-01-01

    An attractive cell source for cartilage tissue engineering, human adipose-derived stem cells (hASCs) can be easily expanded and signaled to differentiate into chondrocytes. This study explores the influence of growth factor distribution and release kinetics on cartilage formation within 3D hASC constructs incorporated with transforming growth factor-β1 (TGF-β1)-loaded gelatin microspheres. The amounts of microspheres, TGF-β1 concentration, and polymer degradation rate were varied within hASC aggregates. Microsphere and TGF-β1 loading concentrations were identified that resulted in glycosaminoglycan (GAG) production comparable to those of control aggregates cultured in TGF-β1-containing medium. Self-assembling hASC sheets were then engineered for the production of larger, more clinically relevant constructs. Chondrogenesis was observed in hASC-only sheets cultured with exogenous TGF-β1 at 3 weeks. Importantly, sheets with incorporated TGF-β1-loaded microspheres achieved GAG production similar to sheets treated with exogenous TGF-β1. Cartilage formation was confirmed histologically via observation of cartilage-like morphology and GAG staining. This is the first demonstration of the self-assembly of hASCs into high-density cell sheets capable of forming cartilage in the presence of exogenous TGF-β1 or with TGF-β1-releasing microspheres. Microsphere incorporation may bypass the need for extended in vitro culture, potentially enabling hASC sheets to be implanted more rapidly into defects to regenerate cartilage in vivo. PMID:24873753

  2. Molecular cloning of pigeon UDP-galactose:beta-D-galactoside alpha1,4-galactosyltransferase and UDP-galactose:beta-D-galactoside beta1,4-galactosyltransferase, two novel enzymes catalyzing the formation of Gal alpha1-4Gal beta1-4Gal beta1-4GlcNAc sequence.

    PubMed

    Suzuki, Noriko; Yamamoto, Kazuo

    2010-02-19

    We previously found that pigeon IgG possesses unique N-glycan structures that contain the Gal alpha1-4Gal beta1-4Gal beta1-4GlcNAc sequence at their nonreducing termini. This sequence is most likely produced by putative alpha1,4- and beta1,4-galactosyltransferases (GalTs), which are responsible for the biosynthesis of the Gal alpha1-4Gal and Gal beta1-4Gal sequences on the N-glycans, respectively. Because no such glycan structures have been found in mammalian glycoproteins, the biosynthetic enzymes that produce these glycans are likely to have distinct substrate specificities from the known mammalian GalTs. To study these enzymes, we cloned the pigeon liver cDNAs encoding alpha4GalT and beta4GalT by expression cloning and characterized these enzymes using the recombinant proteins. The deduced amino acid sequence of pigeon alpha4GalT has 58.2% identity to human alpha4GalT and 68.0 and 66.6% identity to putative alpha4GalTs from chicken and zebra finch, respectively. Unlike human and putative chicken alpha4GalTs, which possess globotriosylceramide synthase activity, pigeon alpha4GalT preferred to catalyze formation of the Gal alpha1-4Gal sequence on glycoproteins. In contrast, the sequence of pigeon beta4GalT revealed a type II transmembrane protein consisting of 438 amino acid residues, with no significant homology to the glycosyltransferases so far identified from mammals and chicken. However, hypothetical proteins from zebra finch (78.8% identity), frogs (58.9-60.4%), zebrafish (37.1-43.0%), and spotted green pufferfish (43.3%) were similar to pigeon beta4GalT, suggesting that the pigeon beta4GalT gene was inherited from the common ancestors of these vertebrates. The sequence analysis revealed that pigeon beta4GalT and its homologs form a new family of glycosyltransferases.

  3. 1-N-glycyl beta-oligosaccharide derivatives as stable intermediates for the formation of glycoconjugate probes.

    PubMed

    Manger, I D; Rademacher, T W; Dwek, R A

    1992-11-10

    Incubation of reducing sugars in ammonium bicarbonate was found to be a simple procedure for the formation of beta-D-glycosylamines of purified complex oligosaccharides in 70-80% yield. These provide valuable intermediates for the synthesis of a wide range of oligosaccharide probes and derivatives by acylation of the 1-amino function. The 1-amino function showed different rates of reactivity with different reagents. In general, interactions with large ring systems such as the fluorophores dansyl chloride and carboxyfluorescein gave 10-20% yields of products, which consisted of mixtures of both anomeric forms, whereas smaller acylating reagents gave near-quantitative yields of the desired beta-D-derivatives. Steric effects may explain differences in reactivity. N-Chloroacetamido derivatives could be obtained in high yield with retention of the beta-anomeric configuration. Subsequent ammonolysis of the chloroacetamido function afforded the corresponding N-glycyl beta-derivatives. The linker thereby introduced retains the amino function, possesses the useful properties of fixed anomeric configuration, improved stability, and uniform reactivity with a variety of reagents, and is structurally analogous to an asparagine side chain. The potential therefore exists for the generation of oligosaccharide derivatives tailored for different applications.

  4. Rubella - Fact Sheet for Parents

    MedlinePlus

    ... this page: About CDC.gov . Redirect for the Rubella fact sheet page. The current fact sheet can ... http://www.cdc.gov/vaccines/parents/diseases/child/rubella.html Print page Share Compartir File Formats Help: ...

  5. Does Long-Term Administration of a Beta-Blocker (Timolol) Induce Fibril-Based Cataract Formation In-vivo?

    PubMed Central

    Nikbakht, Mohammad Reza; Ashrafi-Kooshk, Mohammad Reza; Jaafari, Morteza; Ghasemi, Moosa; Khodarahmi, Reza

    2014-01-01

    Timolol is a non-selective beta-adrenergic receptor antagonist administered for treating glaucoma, heart attacks and hypertension. In the present study, we set out to determine whether or not timolol can provoke cataract formation, thus the influence of timolol on the amyloid-type aggregation of crystallin was investigated. We then provided experimental evidence of crystallin aggregation and its induction by timolol using different spectroscopic measurements. Turbidimetric measurements as well as ThT fluorescence data indicated that timolol induce extent of crystallin amyloid formation. The kinetic of protein aggregation was also changed in presence of increasing concentrations of the drug suggesting that long-term drug administration may contribute to the development of cataract. Since the consequence of timolol-crystallin interaction has yet to be identified, additional data on it may help us to postpone amyloid cataract formation. PMID:25237356

  6. Characterization of Sheet Fracture Patterns in Polygonal-Jointed Lavas at Kokostick Butte, OR, and Mazama Ridge, WA: Investigation and Interpretation of Their Formation and Significance

    NASA Astrophysics Data System (ADS)

    Lodge, R. W.; Lescinsky, D. T.

    2006-12-01

    Polygonal joints in lava flows ("columns") are commonly equant leading to a model of formation associated with cooling in an isotropic stress field. This model, however, does not explain rectangular columns, sheet-like fractures, fractures with crosscutting relationships, and fractures with orientations other than perpendicular to the cooling surface. These fracture patterns are often observed at glaciated volcanoes. The presence of preferential fracture orientations suggests an applied stress component likely due to environmental conditions such as the presence of glaciers or flow dynamics such as down-slope settling or flow margin inflation. During this study we investigated the formation and significance of these non-equant fracture patterns to propose a model for their formation. These `abnormal' fracture patterns have not been discussed in the literature and may be important to better understanding the cooling conditions of such lava flows. To test these possibilities we studied Kokostick Butte dacite flow, OR (near South Sister), and Mazama Ridge andesite flow at Mount Rainier, WA. Both of these flows have well developed sheet-like fractures and display evidence of ice-contact during eruption and emplacement. Sheet fractures are long and continuous fractures that have perpendicular connecting fractures forming rectangular columns. The sheet-like fractures are largely parallel to each other on the exposure surface and the connecting fractures vary locally from primary fractures (associated with cooling toward flow interior) to secondary fractures (associated with cooling by water infiltration). Detailed measurements of fracture orientations and spacing were collected at Kokostick Butte and Mazama Ridge to examine the relationship between the sheet fractures and flow geometry. Preliminary results support this relationship and suggest these patterns likely form due to shear associated with small amounts of flow advance by the rapidly cooling lava. Laboratory

  7. Separation of drug stereoisomers by the formation of. beta. -cyclodextrin inclusion complexes

    SciTech Connect

    Armstrong, D.W.; Ward, T.J.; Armstrong, R.D.; Beesley, T.E.

    1986-05-30

    For many drugs, only racemic mixtures are available for clinical use. Because different stereoisomers of drugs often cause different physiological responses, the use of pure isomers could elicit more exact therapeutic effects. Differential complexation of a variety of drug stereoisomers by immobilized ..beta..-cyclodextrin was investigated. Chiral recognition and racemic resolution were observed with a number of compounds from such clinically useful classes as ..beta..-blockers, calcium-channel blockers, sedative hypnotics, antihistamines, anticonvulsants, diuretics, and synthetic opiates. Separation of the diastereomers of the cardioactive and antimalarial cinchona alkaloids and of two antiestrogens was demonstrated as well. Three dimensional projections of ..beta..-cyclodextrin complexes of propanol, which is resolved by this technique, and warfarin, which is not, are compared. These studies have improved the understanding and application of the chiral interactions of ..beta..-cyclodextrin, and they have demonstrated a means to measure optical purity and to isolate or produce pure enantiomers of drugs. In addition, this highly specific technique could also be used in the pharmacological evaluation of enantiometric drugs. 27 references, 3 figures, 2 tables.

  8. SILICON CARBIDE DATA SHEETS

    DTIC Science & Technology

    These data sheets present a compilation of a wide range of electrical, optical and energy values for alpha and beta- silicon carbide in bulk and film...spectrum. Energy data include energy bands, energy gap and energy levels for variously-doped silicon carbide , as well as effective mass tables, work

  9. Triggers for β-sheet formation at the hydrophobic-hydrophilic interface: high concentration, in-plane orientational order, and metal ion complexation.

    PubMed

    Hoernke, Maria; Falenski, Jessica A; Schwieger, Christian; Koksch, Beate; Brezesinski, Gerald

    2011-12-06

    Amyloid formation plays a causative role in neurodegenerative diseases such as Alzheimer's disease or Parkinson's disease. Soluble peptides form β-sheets that subsequently rearrange into fibrils and deposit as amyloid plaques. Many parameters trigger and influence the onset of the β-sheet formation. Early stages are recently discussed to be cell-toxic. Aiming at understanding various triggers such as interactions with hydrophobic-hydrophilic interfaces and metal ion complexation and their interplay, we investigated a set of model peptides at the air-water interface. We are using a general approach to a variety of diseases such as Alzheimer's disease, Parkinson's disease, and type II diabetes that are connected to amyloid formation. Surface sensitive techniques combined with film balance measurements have been used to assess the conformation of the peptides and their orientation at the air-water interface (IR reflection-absorption spectroscopy). Additionally, the structures of the peptide layers were characterized by grazing incidence X-ray diffraction and X-ray reflectivity. The peptides adsorb to the air-water interface and immediately adopt an α-helical conformation. This helical intermediate transforms into β-sheets upon further triggering. The factors that result in β-sheet formation are dependent on the peptide sequence. In general, the interface has the strongest effect on peptide conformation compared to high concentrations or metal ions. Metal ions are able to prevent aggregation in bulk but not at the interface. At the interface, metal ion complexation has only minor effects on the peptide secondary structure, influencing the in-plane structure that is formed in two dimensions. At the air-water interface, increased concentrations or a parallel arrangement of the α-helical intermediates are the most effective triggers. This study reveals the role of various triggers for β-sheet formation and their complex interplay. Our main finding is that the

  10. Film formation and paper coating with poly ([beta]-hydroxyalkanoate), a biodegradable latex

    SciTech Connect

    Lauzier, C.A.; Monasterios, C.J.; Saracovan, I.; Marchessault, R.H. ); Ramsay, B.A. )

    1993-05-01

    An aqueous latex of a poly ([beta]-hydroxyalkanoate) (PHA) coated on paper imparted water imperviousness without changing mechanical properties. Hot-pressed films biodegraded faster than solvent cast films. The PHA coating on paper degraded totally in activated sludge within 12 days, leaving the cellulose matrix relatively untouched. Blends of PHA latexes with sodium carboxymethl cellulose, polystyrene latex, carboxylated styrenel butadiene latex, natural rubber latex, carboxylated styrenel butadiene latex; natural rubber latex, and starch powders form satisfactory films at room temperature.

  11. Study of the {alpha}{yields}{beta} phase transformation of a Ti-6Al-4V sheet by means of texture change

    SciTech Connect

    Gey, N.; Humbert, M.; Moustahfid, H.

    2000-02-01

    Although a large number of studies on the {alpha}/{beta} phase transformation in titanium alloys have been reported, only a few works deal with the texture change observed during the {alpha}{yields}{beta} transformation during continuous heating. This is due to the difficulty to obtain information about the metallurgical state of the high temperature {beta} phase, which is not stable at room temperature. In pure titanium, the hcp {alpha} phase generally transforms into the bcc {beta} phase according to the Burgers relation with sometimes orientation variant selections. In the case of Ti-6Al-4V alloy, the transformation of the {alpha} phase is performed in the presence of a low volume fraction of {beta} phase which can influence the transformation mechanism. In the present paper, the {alpha}{yields}{beta} texture change of Ti-6Al-4V material is characterized using adapted methods. The resulting textures allows us to discuss the influence of the residual {beta} phase on the transition texture.

  12. Synthetic peptides corresponding to human follicle-stimulating hormone (hFSH)-beta-(1-15) and hFSH-beta-(51-65) induce uptake of 45Ca++ by liposomes: evidence for calcium-conducting transmembrane channel formation

    SciTech Connect

    Grasso, P.; Santa-Coloma, T.A.; Reichert, L.E. Jr. )

    1991-06-01

    We have previously described FSH receptor-mediated influx of 45Ca++ in cultured Sertoli cells from immature rats and receptor-enriched proteoliposomes via activation of voltage-sensitive and voltage-independent calcium channels. We have further shown that this effect of FSH does not require cholera toxin- or pertussis toxin-sensitive guanine nucleotide binding protein or activation of adenylate cyclase. In the present study, we have identified regions of human FSH-beta-subunit which appear to be involved in mediating calcium influx. We screened 11 overlapping peptide amides representing the entire primary structure of hFSH-beta-subunit for their effects on 45Ca++ flux in FSH receptor-enriched proteoliposomes. hFSH-beta-(1-15) and hFSH-beta-(51-65) induced uptake of 45Ca++ in a concentration-related manner. This effect of hFSH-beta-(1-15) and hFSH-beta-(51-65) was also observed in liposomes lacking incorporated FSH receptor. Reducing membrane fluidity by incubating liposomes (containing no receptor) with hFSH-beta-(1-15) or hFSH-beta-(51-65) at temperatures lower than the transition temperatures of their constituent phospholipids resulted in no significant (P greater than 0.05) difference in 45Ca++ uptake. The effectiveness of the calcium ionophore A23187, however, was abolished. Ruthenium red, a voltage-independent calcium channel antagonist, was able to completely block uptake of 45Ca++ induced by hFSH-beta-(1-15) and hFSH-beta-(51-65) whereas nifedipine, a calcium channel blocker specific for L-type voltage-sensitive calcium channels, was without effect. These results suggest that in addition to its effect on voltage-sensitive calcium channel activity, interaction of FSH with its receptor may induce formation of transmembrane aqueous channels which also facilitate influx of extracellular calcium.

  13. Controllable formation of graphene and graphene oxide sheets using photo-catalytic reduction and oxygen plasma treatment

    NASA Astrophysics Data System (ADS)

    Ostovari, Fatemeh; Abdi, Yaser; Ghasemi, Foad

    2012-12-01

    Au/SiO2/Si interdigital electrodes with thickness of 1 μm were created on silicon substrate. Graphene oxide (GO) sheets hanging from these electrodes were obtained by spin coating of chemically synthesized GO dispersed in water. We used UV-light-induced photo-catalytic activity of titanium oxide nanoparticles to reduce the GO layer. Effects of the photo-induced chemical reduction on the conductivity of the GO were investigated. Also, low power DC plasma was used for oxidation of the sheets. Oxygen bombardment leads to sheets with low electrical conductivity. Measurements show that graphene and GO sheets with the controlled electrical conductivity were obtained by these processes. Scanning electron and atomic force microscopy were used to study the morphology of the TiO2/GO and graphene structures. X-ray diffraction and Raman scattering analysis were used to verify the structural characteristics of the prepared sheets. Analysis showed a gradual increase in the number of C-O bonds on the surface of the graphene layer as a result of increasing the time of plasma bombardment. Based on the Raman spectroscopy, the photo-catalytic activity of TiO2 nanoparticles resulted in a decrease in the number of C-O bonds.

  14. Dynamic Current Sheet Formation and Evolution with Application to Inter-(Super)granular Flow Lanes and Quasi-Homologous Jet Activity

    NASA Astrophysics Data System (ADS)

    Edmondson, Justin K.; Velli, M.

    2011-05-01

    The coronal magnetic field structure is an immensely complex system constantly driven away from equilibrium by global drivers such as photospheric flow, flux emergence/cancellation at the lower boundary, helicity injection and transport, etc. In low-beta plasma systems, such as solar corona, the Maxwell stresses dominate forces and therefore the system dynamics. General Poynting stress injection (i.e., flux injection, helicity injection, translational motions, or any combination thereof) results in (possibly large) geometric deformations of the magnetic field, such that the Maxwell stresses distribute as uniformly as possible, constrained by the distorted geometry and topology of the bounding separatricies. Since the topological connectivity is discontinuous across these separatrix surfaces, the magnetic stresses will be discontinuous there as well, manifesting as current sheets within the field. The solar magnetic field undergoes major geometric expansion passing from the photosphere, through the chromosphere, into the corona. No matter the specific details, a mixed polarity distribution at the lower boundary and the divergence-free condition require invariant topological features such as an X-line and separatricies to exist between fields emanating from separate regions of the photosphere. We present the results of fully-3D numerical simulations of a simplified low-beta model of this field expansion. A symmetric injection of Maxwell stresses into this geometry inflates strongly line-tied fields, generating a region of large current densities and magnetic energy dissipation. Elsewhere the injected stresses accumulate along the existing separatricies. There is no evidence of reconnection dynamics until after the initial left-right parity is broken. Once the symmetry breaks, the X-line deforms explosively into a Syrovatskii-type current sheet, leading to a succession of quasi-homologous jet dynamics. The bursty-oscillations of these jets occur as the stresses within

  15. Estrogen receptor-beta colocalizes extensively with parvalbumin-labeled inhibitory neurons in the cortex, amygdala, basal forebrain, and hippocampal formation of intact and ovariectomized adult rats.

    PubMed

    Blurton-Jones, Mathew; Tuszynski, Mark H

    2002-10-21

    Estrogen has been reported to regulate the activity of gamma-aminobutyric acid (GABA)ergic interneurons within the hippocampus, basal forebrain, and hypothalamus of adult rodents. Although estrogen receptor-alpha bearing GABAergic interneurons have been identified previously, the neurotransmitter phenotype of cells that express the more recently characterized estrogen receptor-beta (ER-beta) has not been examined in vivo. We, therefore, have used fluorescent immunohistochemistry to further characterize the phenotype of ER-beta-bearing cells by double labeling for the GABAergic-associated calcium-binding protein, parvalbumin (PV). We find that a large proportion of ER-beta-immunoreactive cells within the cortex, amygdala, basal forebrain, and hippocampal formation of intact and ovariectomized (ovx) adult rats are PV-immunoreactive. Within the infralimbic, agranular insular, primary motor, parietal association, perirhinal, and lateral entorhinal cortices, an average of 95.6% +/- 0.8% (intact) and 94.5% +/- 1.4% (ovx) of all ER-beta-immunoreactive cells coexpress parvalbumin, and this proportion is strikingly similar across these diverse cortical regions. ER-beta/PV double-labeled cells represent 23.3% +/- 1.6% (intact) and 25.8% +/- 2.0% (ovx) of all PV-labeled cells within these regions. ER-beta/PV double-labeled cells are also observed within the lateral, accessory basal, and posterior cortical nuclei of the amygdala, and periamygdaloid cortex. Within the basal forebrain, 31.0% +/- 3.1% (intact) and 26.0% +/- 5.2 % (ovx) of ER-beta-immunoreactive cells coexpress PV. Almost all ER-beta-immunoreactive cells within the subiculum, a major output region of the hippocampal formation, double label for PV (intact = 97.2% +/- 2.8%; ovx = 100% +/- 0.0%). Thus, ER-beta exhibits extensive colocalization with a subclass of inhibitory neurons, suggesting a potential mechanism whereby estrogen can regulate neuronal excitability in diverse and broad brain regions by modulating

  16. Formation of alpha and beta tantalum at the variation of magnetron sputtering conditions

    NASA Astrophysics Data System (ADS)

    Nasakina, E. O.; Sevostyanov, M. A.; Mikhaylova, A. B.; Baikin, A. S.; Sergienko, K. V.; Leonov, A. V.; Kolmakov, A. G.

    2016-02-01

    Nano- and microdimensional surface layers of α and β tantalum on flat NiTi, Ti, glass, etc. substrates were created. Structure and composition of samples were defined by SEM, AES and x-ray diffractometry. With increase in deposition time surface layer thickness not linearly increases. The transitional layer provide high adhesion of a surface layer to a substrate. Irrespective of summary sputtering time the β phase is formed in the beginning and at sputtering time more than 20 min on it α tantalum is deposited, while temperature remains below 150°C. Keywords: composite materials, surface layer, tantalum, alpha and beta phase, nitinol, corrosion resistance.

  17. Inhibition of beta-amyloid aggregation by fluorescent dye labels

    NASA Astrophysics Data System (ADS)

    Amaro, Mariana; Wellbrock, Thorben; Birch, David J. S.; Rolinski, Olaf J.

    2014-02-01

    The fluorescence decay of beta-amyloid's (Aβ) intrinsic fluorophore tyrosine has been used for sensing the oligomer formation of dye-labelled Aβ monomers and the results compared with previously studied oligomerization of the non-labelled Aβ peptides. It has been demonstrated that two different sized, covalently bound probes 7-diethylaminocoumarin-3-carbonyl and Hilyte Fluor 488 (HLF), alter the rate and character of oligomerization to different extents. The ability of HLF to inhibit formation of highly ordered structures containing beta-sheets was also shown. The implications of our findings for using fluorescence methods in amyloidosis research are discussed and the advantages of this auto-fluorescence approach highlighted.

  18. Beta- Lactam Antibiotics Stimulate Biofilm Formation in Non-Typeable Haemophilus influenzae by Up-Regulating Carbohydrate Metabolism

    PubMed Central

    Wu, Siva; Li, Xiaojin; Gunawardana, Manjula; Maguire, Kathleen; Guerrero-Given, Debbie; Schaudinn, Christoph; Wang, Charles; Baum, Marc M.; Webster, Paul

    2014-01-01

    Non-typeable Haemophilus influenzae (NTHi) is a common acute otitis media pathogen, with an incidence that is increased by previous antibiotic treatment. NTHi is also an emerging causative agent of other chronic infections in humans, some linked to morbidity, and all of which impose substantial treatment costs. In this study we explore the possibility that antibiotic exposure may stimulate biofilm formation by NTHi bacteria. We discovered that sub-inhibitory concentrations of beta-lactam antibiotic (i.e., amounts that partially inhibit bacterial growth) stimulated the biofilm-forming ability of NTHi strains, an effect that was strain and antibiotic dependent. When exposed to sub-inhibitory concentrations of beta-lactam antibiotics NTHi strains produced tightly packed biofilms with decreased numbers of culturable bacteria but increased biomass. The ratio of protein per unit weight of biofilm decreased as a result of antibiotic exposure. Antibiotic-stimulated biofilms had altered ultrastructure, and genes involved in glycogen production and transporter function were up regulated in response to antibiotic exposure. Down-regulated genes were linked to multiple metabolic processes but not those involved in stress response. Antibiotic-stimulated biofilm bacteria were more resistant to a lethal dose (10 µg/mL) of cefuroxime. Our results suggest that beta-lactam antibiotic exposure may act as a signaling molecule that promotes transformation into the biofilm phenotype. Loss of viable bacteria, increase in biofilm biomass and decreased protein production coupled with a concomitant up-regulation of genes involved with glycogen production might result in a biofilm of sessile, metabolically inactive bacteria sustained by stored glycogen. These biofilms may protect surviving bacteria from subsequent antibiotic challenges, and act as a reservoir of viable bacteria once antibiotic exposure has ended. PMID:25007395

  19. Anatomy and controlling factors of a Late Cretaceous Aeolian sand sheet: The Marília and the Adamantina formations, NW Bauru Basin, Brazil

    NASA Astrophysics Data System (ADS)

    Basilici, Giorgio; Führ Dal'Bó, Patrick Francisco

    2010-04-01

    Few previous studies have given significant consideration to the palaeosols in aeolian sand sheet sedimentary successions and, mainly, to their palaeoenvironmental and stratigraphic meaning in interaction with the deposits. These themes are considered in this study that deals with the depositional architecture and the factors controlling the construction, accumulation and preservation of an ancient aeolian sand sheet, that forms part of the Adamantina and Marília formations, in the Bauru Basin (Late Cretaceous, Brazil). In the NW portion of the Bauru Basin, these two units, ca 220 m thick, consist of sandstone, and secondarily of sandy conglomerate and mudstone, and are characterised by vertically alternated palaeosols and deposits. Facies analyses of the deposits and macroscopic characterisation of the palaeosols in 45 outcrops were integrated with laboratory analyses that consisted in descriptions of slabs of rock samples, petrographic analyses, clay mineralogy determination, geochemical analyses of the major oxides, and micromorphological characterisation of the palaeosols. Three architectural elements were recognised: palaeosols, wind-ripple-dominated aeolian sand sheet deposits, and ephemeral river deposits. The palaeosols constitute 66% of the entire sedimentary succession, and consist principally of Aridisols and, subordinately, of Alfisols, Vertisols, and Entisols. The wind-ripple-dominated aeolian sand sheet deposits (25%) are composed of sandstone, organised in translatent climbing wind-ripple strata, and secondarily of sandstone and mudstone deposited by infrequent floods. The ephemeral river deposits (9%) consist of sandy conglomerates 4 m thick and ca 2 km wide. Wind-ripple-dominated aeolian sand sheet deposits formed during relatively dry climate period on an unstable topographic surface of an aeolian sand sheet, where aeolian deposition or erosion prevailed. Palaeosols and ephemeral river deposits formed in a more humid climate period on a stable

  20. Chimeric DNA-RNA hammerhead ribozyme targeting transforming growth factor-beta 1 mRNA inhibits neointima formation in rat carotid artery after balloon injury.

    PubMed

    Ando, Hideyuki; Fukuda, Noboru; Kotani, Motoko; Yokoyama, Shin ichiro; Kunimoto, Satoshi; Matsumoto, Koichi; Saito, Satoshi; Kanmatsuse, Katsuo; Mugishima, Hideo

    2004-01-12

    We designed and synthesized a chimeric DNA-RNA hammerhead ribozyme targeting transforming growth factor (TGF)-beta 1 mRNA and found that this ribozyme effectively and specifically inhibited growth of vascular smooth muscle cells. We examined the effects of the chimeric DNA-RNA hammerhead ribozyme targeting TGF-beta 1 mRNA on neointima formation and investigated the underlying mechanism to develop a possible gene therapy for coronary artery restenosis after percutaneous transluminal coronary angioplasty. Expression of mRNAs encoding TGF-beta 1, p27kip1, and connective tissue growth factor (CTGF) in carotid artery increased after balloon injury. Fluorescein-isothiocyanate (FITC)-labeled ribozyme was taken up into the midlayer smooth muscle of the injured carotid artery. Both 2 and 5 mg of ribozyme reduced neointima formation by 65% compared to that of controls. Ribozyme markedly decreased expression of TGF-beta 1 mRNA and protein in injured vessel. Mismatch ribozyme had no effect on expression of TGF-beta 1 mRNA protein in injured vessel. Ribozyme markedly decreased expression of fibronectin, p27kip1, and CTGF mRNAs in injured vessel, whereas a mismatch ribozyme had no effect on these mRNAs. These findings indicate that the chimeric DNA-RNA hammerhead ribozyme targeting TGF-beta 1 mRNA inhibits neointima formation in rat carotid artery after balloon injury with suppression of TGF-beta 1 and inhibition of extracellular matrix and CTGF. In conclusion, the hammerhead ribozyme against TGF-beta 1 may have promise as a therapy for coronary artery restenosis after percutaneous transluminal coronary angioplasty.

  1. Formation of high-{beta} plasma and stable confinement of toroidal electron plasma in Ring Trap 1

    SciTech Connect

    Saitoh, H.; Yoshida, Z.; Morikawa, J.; Furukawa, M.; Yano, Y.; Kawai, Y.; Kobayashi, M.; Vogel, G.; Mikami, H.

    2011-05-15

    Formation of high-{beta} electron cyclotron resonance heating plasma and stable confinement of pure electron plasma have been realized in the Ring Trap 1 device, a magnetospheric configuration generated by a levitated dipole field magnet. The effects of coil levitation resulted in drastic improvements of the confinement properties, and the maximum local {beta} value has exceeded 70%. Hot electrons are major component of electron populations, and its particle confinement time is 0.5 s. Plasma has a peaked density profile in strong field region [H. Saitoh et al., 23rd IAEA Fusion Energy Conference EXC/9-4Rb (2010)]. In pure electron plasma experiment, inward particle diffusion is realized, and electrons are stably trapped for more than 300 s. When the plasma is in turbulent state during beam injection, plasma flow has a shear, which activates the diocotron (Kelvin-Helmholtz) instability. The canonical angular momentum of the particle is not conserved in this phase, realizing the radial diffusion of charged particles across closed magnetic surfaces. [Z. Yoshida et al., Phys Rev. Lett. 104, 235004 (2010); H. Saitoh et al., Phys. Plasmas 17, 112111 (2010).].

  2. Formation and accumulation of alpha-acids, beta-acids, desmethylxanthohumol, and xanthohumol during flowering of hops (Humulus lupulus L.).

    PubMed

    De Keukeleire, Jelle; Ooms, Geert; Heyerick, Arne; Roldan-Ruiz, Isabel; Van Bockstaele, Erik; De Keukeleire, Denis

    2003-07-16

    Important secondary metabolites, present in hops (Humulus lupulus L.), include alpha-acids and beta-acids, which are essential for the brewing of beer, as well as the prenylated chalcones, desmethylxanthohumol, and xanthohumol, which exhibit interesting bioactive properties. Their formation and accumulation in five selected hop varieties, Wye Challenger, Wye Target, Golding, Admiral, and Whitbread Golding Variety, were quantitatively monitored by high-performance liquid chromatography using UV detection. All target compounds were present from the onset of flowering, not only in female hop cones but also in male inflorescences, albeit in low concentrations. During development from female inflorescences to cones, levels of alpha-acids, beta-acids, desmethylxanthohumol, and xanthohumol gradually increased, while each hop variety exhibited individual accumulation rates. Furthermore, these compounds were present in leaves of fully grown hops as well. The study demonstrated that key compounds for flavor and potential beneficial health effects associated with beer not only reside in the glandular lupulin structures but also are distributed over various parts of the hop plant.

  3. Beta-sheet secondary structure of the trimeric globular domain of C1q of complement and collagen types VIII and X by Fourier-transform infrared spectroscopy and averaged structure predictions.

    PubMed Central

    Smith, K F; Haris, P I; Chapman, D; Reid, K B; Perkins, S J

    1994-01-01

    C1q plays a key role in the recognition of immune complexes, thereby initiating the classical pathway of complement activation. Although the triple-helix conformation of its N-terminal segment is well established, the secondary structure of the trimeric globular C-terminal domain is as yet unknown. The secondary structures of human C1q and C1q stalks and pepsin-extracted human collagen types I, III and IV (with no significant non-collagen-like structure) were studied by Fourier-transform i.r. spectroscopy in 2H2O buffers. After second-derivative calculation to resolve the fine structure of the broad amide I band, the Fourier-transform i.r. spectrum of C1q showed two major bands, one at 1637 cm-1, which is a characteristic frequency for beta-sheets, and one at 1661 cm-1. Both major bands were also detected for Clq in H2O buffers. Only the second major band was observed at 1655 cm-1 in pepsin-digested C1q which contains primarily the N-terminal triple-helix region. The Fourier-transform i.r. spectra of collagen in 2H2O also showed a major band at 1659 cm-1 (and minor bands at 1632 cm-1 and 1682 cm-1). It is concluded that the C1q globular heads contain primarily beta-sheet structure. The C-terminal domains of C1q show approximately 25% sequence identity with the non-collagen-like C-terminal regions of the short-chain collagen types VIII and X. To complement the Fourier-transform-i.r. spectroscopic data, averaged Robson and Chou-Fasman structure predictions on 15 similar sequences for the globular domains of C1q and collagen types VIII and X were performed. These showed a clear pattern of ten beta-strands interspersed by beta-turns and /or loops. Residues thought to be important for C1q-immune complex interactions with IgG and IgM were predicted to be at a surface-exposed loop. Sequence insertions and deletions, glycosylation sites, the free cysteine residue and RGD recognition sequences were also predicted to be at surface-exposed positions. Images Figure 4 PMID

  4. Evidence for Intramolecular Antiparallel Beta-Sheet Structure in Alpha-Synuclein Fibrils from a Combination of Two-Dimensional Infrared Spectroscopy and Atomic Force Microscopy.

    PubMed

    Roeters, Steven J; Iyer, Aditya; Pletikapić, Galja; Kogan, Vladimir; Subramaniam, Vinod; Woutersen, Sander

    2017-01-23

    The aggregation of the intrinsically disordered protein alpha-synuclein (αS) into amyloid fibrils is thought to play a central role in the pathology of Parkinson's disease. Using a combination of techniques (AFM, UV-CD, XRD, and amide-I 1D- and 2D-IR spectroscopy) we show that the structure of αS fibrils varies as a function of ionic strength: fibrils aggregated in low ionic-strength buffers ([NaCl] ≤ 25 mM) have a significantly different structure than fibrils grown in higher ionic-strength buffers. The observations for fibrils aggregated in low-salt buffers are consistent with an extended conformation of αS molecules, forming hydrogen-bonded intermolecular β-sheets that are loosely packed in a parallel fashion. For fibrils aggregated in high-salt buffers (including those prepared in buffers with a physiological salt concentration) the measurements are consistent with αS molecules in a more tightly-packed, antiparallel intramolecular conformation, and suggest a structure characterized by two twisting stacks of approximately five hydrogen-bonded intermolecular β-sheets each. We find evidence that the high-frequency peak in the amide-I spectrum of αS fibrils involves a normal mode that differs fundamentally from the canonical high-frequency antiparallel β-sheet mode. The high sensitivity of the fibril structure to the ionic strength might form the basis of differences in αS-related pathologies.

  5. Formation of catechol estrogen glutathione conjugates and gamma-glutamyl transpeptidase-dependent nephrotoxicity of 17beta-estradiol in the golden Syrian hamster.

    PubMed

    Butterworth, M; Lau, S S; Monks, T J

    1997-03-01

    In an animal model of hormone-mediated carcinogenesis, male golden Syrian hamsters develop renal carcinoma following prolonged exposure to 17beta-estradiol. The basis for the species and tissue specificity is unclear. Detailed information on the disposition of 17beta-estradiol in this model is lacking. Because catechol estrogens have been implicated in this model of carcinogenesis, we investigated the metabolism and nephrotoxicity of 17beta-estradiol in golden Syrian hamsters, with emphasis on the formation of catechol estrogen thioethers. 17beta-Estradiol (50 micromol/kg, i.p.) is a mild nephrotoxicant, causing significant elevations in the urinary excretion of gamma-glutamyl transpeptidase (gamma-GT), alkaline phosphatase, glutathione S-transferase (GST) and glucose. Increases in renal protein carbonyls and lipid hydroperoxides, which are markers of oxidative damage, also occur after administration of 17beta-estradiol (50 micromol/kg, i.p.). 17beta-Estradiol-mediated nephrotoxicity is reduced by treating animals with acivicin, an inhibitor of gamma-GT, implying that toxicity is mediated by metabolites requiring metabolism by this enzyme. Following administration of 17beta-[14C]estradiol (100 micromol/kg) to hamsters, 9.7% of the dose is recovered in bile after 5 h, the majority (7.9%) representing aqueous metabolites. Seven catechol estrogen GSH conjugates were identified, 2-hydroxy-1,4-bis-(glutathion-S-yl)-17beta-estradiol, 2-hydroxy-4-(glutathion-S-yl)-17beta-estradiol, 2-hydroxy-4-(glutathion-S-yl)-estrone, 4-hydroxy-1-(glutathion-S-yl)-estrone, 2-hydroxy-1-(glutathion-S-yl)-estrone, 4-hydroxy-1-(glutathion-S-yl)-17beta-estradiol, and 2-hydroxy-1-(glutathion-S-yl)-17beta-estradiol. At 5.4 micromol/kg of 17beta-estradiol, a dose-reflective of daily exposure levels in the hamster model of nephrocarcinogenicity, 12% of the dose is recovered within 5 h as a combination of GSH conjugates of 2- and 4-hydroxy-17beta-estradiol and 2- and 4-hydroxyestrone. In summary

  6. Beta2-amino acids-syntheses, occurrence in natural products, and components of beta-peptides1,2.

    PubMed

    Lelais, Gérald; Seebach, Dieter

    2004-01-01

    Although they are less abundant than their alpha-analogues, beta-amino acids occur in nature both in free form and bound to peptides. Oligomers composed exclusively of beta-amino acids (so-called beta-peptides) might be the most thoroughly investigated peptidomimetics. Beside the facts that they are stable to metabolism, exhibit slow microbial degradation, and are inherently stable to proteases and peptidases, they fold into well-ordered secondary structures consisting of helices, turns, and sheets. In this respect, the most intriguing effects have been observed when beta2-amino acids are present in the beta-peptide backbone. This review gives an overview of the occurrence and importance of beta2-amino acids in nature, placing emphasis on the metabolic pathways of beta-aminoisobutyric acid (beta-Aib) and the appearance of beta2-amino acids as secondary metabolites or as components of more complex natural products, such as peptides, depsipeptides, lactones, and alkaloids. In addition, a compilation of the syntheses of both achiral and chiral beta2-amino acids is presented. While there are numerous routes to achiral beta2-amino acids, their EPC synthesis is currently the subject of many investigations. These include the diastereoselective alkylation and Mannich-type reactions of cyclic- or acyclic beta-homoglycine derivatives containing chiral auxiliaries, the Curtius degradation, the employment of transition-metal catalyzed reactions such as enantioselective hydrogenations, reductions, C-H insertions, and Michael-type additions, and the resolution of rac. beta2-amino acids, as well as several miscellaneous methods. In the last part of the review, the importance of beta2-amino acids in the formation of beta-peptide secondary structures is discussed.

  7. Pattern formation in icosahedral virus capsids: the papova viruses and Nudaurelia capensis beta virus.

    PubMed Central

    Marzec, C J; Day, L A

    1993-01-01

    The capsids of the spherical viruses all show underlying icosahedral symmetry, yet they differ markedly in capsomere shape and in capsomere position and orientation. The capsid patterns presented by the capsomere shapes, positions, and orientations of three viruses (papilloma, SV40, and N beta V) have been generated dynamically through a bottom-up procedure which provides a basis for understanding the patterns. A capsomere shape is represented in two-dimensional cross-section by a mass or charge density on the surface of a sphere, given by an expansion in spherical harmonics, and referred to herein as a morphological unit (MU). A capsid pattern is represented by an icosahedrally symmetrical superposition of such densities, determined by the positions and orientations of its MUs on the spherical surface. The fitness of an arrangement of MUs is measured by an interaction integral through which all capsid elements interact with each other via an arbitrary function of distance. A capsid pattern is generated by allowing the correct number of approximately shaped MUs to move dynamically on the sphere, positioning themselves until an extremum of the fitness function is attained. The resulting patterns are largely independent of the details of both the capsomere representation and the interaction function; thus the patterns produced are generic. The simplest useful fitness function is sigma 2, the average square of the mass (or charge) density, a minimum of which corresponds to a "uniformly spaced" MU distribution; to good approximation, the electrostatic free energy of charged capsomeres, calculated from the linearized Poisson-Boltzmann equation, is proportional to sigma 2. With disks as MUs, the model generates the coordinated lattices familiar from the quasi-equivalence theory, indexed by triangulation numbers. Using fivefold MUs, the model generates the patterns observed at different radii within the T = 7 capsid of papilloma and at the surface of SV40; threefold MUs

  8. [The effect of a simulated inflammation procedure in simulated body fluid on bone-like apatite formation on porous HA/beta-TCP bioceramics].

    PubMed

    Ji, Jingou; Ran, Junguo; Gou, Li; Wang, Fangfu; Sun, Luwei

    2004-08-01

    The formation of bone-like apatite on porous HA/beta-TCP bioceramics in dynamic simulated body fluid (SBF) undergoing a simulated inflammation procedure (pH = 6.5) was investigated in order to study the mechanism of osteoinduction and build a new method to choose biomaterials with better bioactivity. The results showed that the surface of porous HA/beta-TCP bioceramics which underwent a simulated inflammation procedure in dynamic SBF was more smooth. The light acidity in the simulated inflammation procedure would dissolve the fine grains and the parts possessing smaller curvature radius on the surface of porous HA/beta-TCP bioceramics, which would reduce the bioceramics solubility. Followed in normal SBF (pH = 7.4), the amount of bone-like apatite formed on the porous HA/beta-TCP bioceramics was less than that of porous HA/beta-TCP bioceramics incubation in normal SBF all along. The results also showed that the amount of bone-like apatite formed on the porous HA/beta-TCP bioceramics sintered by a microwave plasma was more than that of porous HA/beta-TCP bioceramics sintered by a conventional furnace.

  9. The roles of THY1 and integrin beta3 in cell adhesion during theca cell layer formation and the effect of follicle-stimulating hormone on THY1 and integrin beta3 localization in mouse ovarian follicles.

    PubMed

    Itami, Saori; Tamotsu, Satoshi; Sakai, Atsushi; Yasuda, Keiko

    2011-05-01

    The mechanism of theca cell layer formation in mammalian ovaries has not been elucidated. In the present study, we examined the roles of THY1 and integrin beta3 in theca cell layer formation during mouse folliculogenesis. The localization pattern of THY1 and integrin beta3 in adult mouse ovary was investigated immunohistochemically. The strongest THY1 signal was observed in theca cell layers from secondary to preantral follicles, at which time theca cells have begun to participate in follicle formation. Integrin beta3 also localized to the theca cell layer of secondary to preantral follicles and showed a localization pattern similar to that of THY1. Moreover, the role of THY1 in theca cell layer formation was examined using a follicle culture system. When anti-THY1 antibody was added to this culture, no theca cell layers were formed, and the granulosa cells were distanced from each other. Because a THY1 signal was not observed in ovaries at stages earlier than prepuberty, THY1 localization also appeared to be affected by mouse development. This possibility was examined by determining the effect of administering follicle-stimulating hormone, luteinizing hormone, and 17beta-estradiol to 7-day-old mice on THY1 localization in the ovary 3 days later. Only follicle-stimulating hormone induced a THY1 signal in 10-day-old mouse ovaries. No THY1 signal was observed in untreated 10-day-old ovaries. In conclusion, THY1 might play a role in cell adhesion via binding to integrin beta3 in mouse ovaries. The present results suggest that THY1 localization may be affected by follicle-stimulating hormone in mouse ovaries.

  10. Role of pyridoxamine in the formation of the Amadori/Heyns compounds and aggregates during the glycation of beta-lactoglobulin with galactose and tagatose.

    PubMed

    Corzo-Martínez, Marta; Moreno, F Javier; Olano, Agustín; Villamiel, Mar

    2010-01-13

    The effect of pyridoxamine on the Maillard reaction during the formation of conjugates of beta-lactoglobulin with galactose and tagatose under controlled conditions (pH 7, 0.44 aw, 40 and 50 degrees C, for 6 days) has been studied, for the first time, by means of the changes in reducing carbohydrates, formation of Amadori or Heyns compounds, and aggregates and browning development. The results showed the formation of interaction products between pyridoxamine and galactose or tagatose either in the presence or in the absence of beta-lactoglobulin, indicating that pyridoxamine competes with the free amino groups of beta-lactoglobulin for the carbonyl group of both carbohydrates. Thus, a small inhibitory effect of pyridoxamine on the initial stages of the Maillard reaction was pointed out. Furthermore, much lower aggregation and color formation rates were observed in the conjugates of beta-lactoglobulin galactose/tagatose with pyridoxamine than without this compound, supporting its potent inhibitory effect on the advanced and final stages of the Maillard reaction. These findings reveal the usefulness of food-grade inhibitors of the advanced stages of the Maillard reaction, such as pyridoxamine, that, in combination with mild storage conditions, could lead to the formation of safer neoglycoconjugates without impairing their nutritional quality.

  11. Dynamics of equilibrium upset and electromagnetic energy transformation in the geomagnetotail: A theory and simulation using particles. 3. Versions of formation of thin current sheets

    NASA Astrophysics Data System (ADS)

    Domrin, V. I.; Kropotkin, A. P.

    2007-10-01

    The final part of the study is devoted to the process of rapid reconfiguration of the geomagnetotail after the upset of the equilibrium, i.e., to substorm activation. Such a version of spontaneous formation of nonlinear kinetic small-scale structures at the site occupied by an initial current sheet (CS), which results in the formation of a specific equilibrium current structure with strong ion anisotropy (forced kinetic current sheet, FKCS), has been revealed in the course of numerical simulation. This reconfiguration “channel” is realized when the relative value of the magnetic field component normal to CS is smaller than a certain critical value. In this case the disturbance intensity is SPONTANEOUSLY settled at a certain final level at the late stages. The obtained results are compared with the previous study of the system evolution under the action of the external trigger. The physical causes and specific features of different CS evolution regimes are considered. The studied plasma mechanisms are responsible for the effects of rapid energy transformation—magnetic field “annihilation”—that took place in the geomagnetotail.

  12. Influence of Interleukin-1 Beta on Platelet-Poor Plasma Clot Formation: A Potential Impact on Early Bone Healing

    PubMed Central

    Masci, Paul P.; Crawford, Ross; Xiao, Yin

    2016-01-01

    Objectives Hematoma quality (especially the fibrin matrix) plays an important role in the bone healing process. Here, we investigated the effect of interleukin-1 beta (IL-1β) on fibrin clot formation from platelet-poor plasma (PPP). Methods Five-milliliter of rat whole-blood samples were collected from the hepatic portal vein. All blood samples were firstly standardized via a thrombelastograph (TEG), blood cell count, and the measurement of fibrinogen concentration. PPP was prepared by collecting the top two-fifths of the plasma after centrifugation under 400 × g for 10 min at 20°C. The effects of IL-1β cytokines on artificial fibrin clot formation from PPP solutions were determined by scanning electronic microscopy (SEM), confocal microscopy (CM), turbidity, and clot lysis assays. Results The lag time for protofibril formation was markedly shortened in the IL-1β treatment groups (243.8 ± 76.85 in the 50 pg/mL of IL-1β and 97.5 ± 19.36 in the 500 pg/mL of IL-1β) compared to the control group without IL-1β (543.8 ± 205.8). Maximal turbidity was observed in the control group. IL-1β (500 pg/mL) treatment significantly decreased fiber diameters resulting in smaller pore sizes and increased density of the fibrin clot structure formed from PPP (P < 0.05). The clot lysis assay revealed that 500 pg/mL IL-1β induced a lower susceptibility to dissolution due to the formation of thinner and denser fibers. Conclusion IL-1β can significantly influence PPP fibrin clot structure, which may affect the early bone healing process. PMID:26909757

  13. Formation of the Maturín Foreland Basin, eastern Venezuela: Thrust sheet loading or subduction dynamic topography

    NASA Astrophysics Data System (ADS)

    JáCome, Maria I.; Kusznir, Nick; Audemard, Felipe; Flint, Steve

    2003-10-01

    The Maturín Basin in eastern Venezuela is considered a good example of a peripheral foreland basin. Earthquake and tomographic data indicate that eastern Venezuela is affected by the oblique subduction of the South American Plate underneath the Caribbean Plate. New forward flexural isostatic modeling of eastern Venezuela has been carried out in order to determine whether the Maturín Basin was generated purely by thrust sheet loading from the Serranía and Monagas Foreland Thrust Belts. A sequence of forward models from middle Miocene to Present was generated for 3 profiles across the Serranía del Interior Thrust Belt, the Monagas Foreland Thrust Belt, and the Maturín Foreland Basin. The predictions of these models are constrained using seismic reflection and well data. The flexural isostatic modeling shows that thrust sheet loading associated with the Serranía del Interior and Monagas Foreland thrust belts is insufficient to generate the observed subsidence within the Maturín Basin. Dynamic fluid flow modeling of subduction related dynamic topography of eastern Venezuela has been used to investigate the influence of South American Plate subduction on the generation of the accommodation space observed in the Maturín Basin. Fluid flow modeling of subduction related dynamic topography suggests that the subduction of the South American lithospheric mantle caused downward deflection of the South American crust affecting the Maturín Basin and the Serranía Thrust Belt. This modeling suggests that the Maturín Basin subsidence has two components: 55% related to thrust sheet loading and 45% driven by continental subduction.

  14. Natalizumab plus interferon beta-1a reduces lesion formation in relapsing multiple sclerosis.

    PubMed

    Radue, Ernst-Wilhelm; Stuart, William H; Calabresi, Peter A; Confavreux, Christian; Galetta, Steven L; Rudick, Richard A; Lublin, Fred D; Weinstock-Guttman, Bianca; Wynn, Daniel R; Fisher, Elizabeth; Papadopoulou, Athina; Lynn, Frances; Panzara, Michael A; Sandrock, Alfred W

    2010-05-15

    The SENTINEL study showed that the addition of natalizumab improved outcomes for patients with relapsing multiple sclerosis (MS) who had experienced disease activity while receiving interferon beta-1a (IFNbeta-1a) alone. Previously unreported secondary and tertiary magnetic resonance imaging (MRI) measures are presented here. Patients received natalizumab 300 mg (n=589) or placebo (n=582) intravenously every 4 weeks plus IFNbeta-1a 30 microg intramuscularly once weekly. Annual MRI scans allowed comparison of a range of MRI end points versus baseline. Over 2 years, 67% of patients receiving natalizumab plus IFNbeta-1a remained free of new or enlarging T2-lesions compared with 30% of patients receiving IFNbeta-1a alone. The mean change from baseline in T2 lesion volume over 2 years decreased in patients receiving natalizumab plus IFNbeta-1a and increased in those receiving IFNbeta-1a alone (-277.5mm(3) versus 525.6mm(3); p<0.001). Compared with IFNbeta-1a alone, add-on natalizumab therapy resulted in a smaller increase in mean T1-hypointense lesion volume after 2 years (1821.3mm(3) versus 2210.5mm(3); p<0.001), a smaller mean number of new T1-hypointense lesions over 2 years (2.3 versus 4.1; p<0.001), and a slower rate of brain atrophy during the second year of therapy (-0.31% versus -0.40%; p=0.020). Natalizumab add-on therapy reduced gadolinium-enhancing, T1-hypointense, and T2 MRI lesion activity and slowed brain atrophy progression in patients with relapsing MS who experienced disease activity despite treatment with IFNbeta-1a alone.

  15. Evidence for Intramolecular Antiparallel Beta-Sheet Structure in Alpha-Synuclein Fibrils from a Combination of Two-Dimensional Infrared Spectroscopy and Atomic Force Microscopy

    PubMed Central

    Roeters, Steven J.; Iyer, Aditya; Pletikapić, Galja; Kogan, Vladimir; Subramaniam, Vinod; Woutersen, Sander

    2017-01-01

    The aggregation of the intrinsically disordered protein alpha-synuclein (αS) into amyloid fibrils is thought to play a central role in the pathology of Parkinson’s disease. Using a combination of techniques (AFM, UV-CD, XRD, and amide-I 1D- and 2D-IR spectroscopy) we show that the structure of αS fibrils varies as a function of ionic strength: fibrils aggregated in low ionic-strength buffers ([NaCl] ≤ 25 mM) have a significantly different structure than fibrils grown in higher ionic-strength buffers. The observations for fibrils aggregated in low-salt buffers are consistent with an extended conformation of αS molecules, forming hydrogen-bonded intermolecular β-sheets that are loosely packed in a parallel fashion. For fibrils aggregated in high-salt buffers (including those prepared in buffers with a physiological salt concentration) the measurements are consistent with αS molecules in a more tightly-packed, antiparallel intramolecular conformation, and suggest a structure characterized by two twisting stacks of approximately five hydrogen-bonded intermolecular β-sheets each. We find evidence that the high-frequency peak in the amide-I spectrum of αS fibrils involves a normal mode that differs fundamentally from the canonical high-frequency antiparallel β-sheet mode. The high sensitivity of the fibril structure to the ionic strength might form the basis of differences in αS-related pathologies. PMID:28112214

  16. Evidence for Intramolecular Antiparallel Beta-Sheet Structure in Alpha-Synuclein Fibrils from a Combination of Two-Dimensional Infrared Spectroscopy and Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Roeters, Steven J.; Iyer, Aditya; Pletikapić, Galja; Kogan, Vladimir; Subramaniam, Vinod; Woutersen, Sander

    2017-01-01

    The aggregation of the intrinsically disordered protein alpha-synuclein (αS) into amyloid fibrils is thought to play a central role in the pathology of Parkinson’s disease. Using a combination of techniques (AFM, UV-CD, XRD, and amide-I 1D- and 2D-IR spectroscopy) we show that the structure of αS fibrils varies as a function of ionic strength: fibrils aggregated in low ionic-strength buffers ([NaCl] ≤ 25 mM) have a significantly different structure than fibrils grown in higher ionic-strength buffers. The observations for fibrils aggregated in low-salt buffers are consistent with an extended conformation of αS molecules, forming hydrogen-bonded intermolecular β-sheets that are loosely packed in a parallel fashion. For fibrils aggregated in high-salt buffers (including those prepared in buffers with a physiological salt concentration) the measurements are consistent with αS molecules in a more tightly-packed, antiparallel intramolecular conformation, and suggest a structure characterized by two twisting stacks of approximately five hydrogen-bonded intermolecular β-sheets each. We find evidence that the high-frequency peak in the amide-I spectrum of αS fibrils involves a normal mode that differs fundamentally from the canonical high-frequency antiparallel β-sheet mode. The high sensitivity of the fibril structure to the ionic strength might form the basis of differences in αS-related pathologies.

  17. Inhibition of islet amyloid polypeptide fibril formation by selenium-containing phycocyanin and prevention of beta cell apoptosis.

    PubMed

    Li, Xiaoling; Ma, Lijuan; Zheng, Wenjie; Chen, Tianfeng

    2014-10-01

    Human islet amyloid polypeptide (hIAPP) fibril is the major constituent of amyloid deposits in pancreatic islets of type 2 diabetes. Misfolding and hIAPP fibril formation are thought to be important in the pathogenesis of diabetes. Studies have showed that selenium-containing phycocyanin (Se-PC) inhibited the fibrillation of hIAPP to form nanoscale particles, which is mainly by interfering with the combination between hIAPP. Small nanoscale oligomers tended to grow into larger nanoparticles and the size of nanoparticles increased with the incubation time. By interfering with the fibrillation of hIAPP and altering the structure, Se-PC alleviated hIAPP-induced cell apoptosis. Meantime, generation of ROS produced during the fibrillation process was inhibited, which was proposed to be the main factor for the hIAPP-cytotoxicity in beta cells. Taken together, Se-PC inhibited hIAPP fibrillation, thus suppressed the formation of ROS to show protective effect on hIAPP mediated cell apoptosis. Our studies provide useful information for our understanding of the interaction mechanisms of Se-PC on hIAPP structure and protective mechanisms on hIAPP cytotoxicity, presenting useful candidate for anti-diabetes drug development.

  18. Evidence for adduct formation at the semiconductor-solution interface. Photoluminescent properties of cadmium selenide in the presence of lanthanide. beta. -diketonate complexes

    SciTech Connect

    Murphy, C.J.; Ellis, A.B. )

    1990-04-05

    Photoluminescence (PL) measurements of etched, single-crystal n-CdSe demonstrate that the semiconductor surface engages in adduct formation with a family of lanthanide {beta}-diketonate complexes, Ln(fod){sub 3} (Ln = lanthanide; fod = 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato anion), in isooctane ambient.

  19. Pauling and Corey's alpha-pleated sheet structure may define the prefibrillar amyloidogenic intermediate in amyloid disease.

    PubMed

    Armen, Roger S; DeMarco, Mari L; Alonso, Darwin O V; Daggett, Valerie

    2004-08-10

    Transthyretin, beta(2)-microglobulin, lysozyme, and the prion protein are four of the best-characterized proteins implicated in amyloid disease. Upon partial acid denaturation, these proteins undergo conformational change into an amyloidogenic intermediate that can self-assemble into amyloid fibrils. Many experiments have shown that pH-mediated changes in structure are required for the formation of the amyloidogeneic intermediate, but it has proved impossible to characterize these conformational changes at high resolution using experimental means. To probe these conformational changes at atomic resolution, we have performed molecular dynamics simulations of these proteins at neutral and low pH. In low-pH simulations of all four proteins, we observe the formation of alpha-pleated sheet secondary structure, which was first proposed by L. Pauling and R. B. Corey [(1951) Proc. Natl. Acad. Sci. USA 37, 251-256]. In all beta-sheet proteins, transthyretin and beta(2)-microglobulin, alpha-pleated sheet structure formed over the strands that are highly protected in hydrogen-exchange experiments probing amyloidogenic conditions. In lysozyme and the prion protein, alpha-sheets formed in the specific regions of the protein implicated in the amyloidogenic conversion. We propose that the formation of alpha-pleated sheet structure may be a common conformational transition in amyloidosis.

  20. Co-translational formation and pharmacological characterization of beta1-adrenergic receptor/nanodisc complexes with different lipid environments.

    PubMed

    Rues, Ralf-Bernhardt; Dötsch, Volker; Bernhard, Frank

    2016-06-01

    G protein-coupled receptors are of key significance for biomedical research. Streamlined approaches for their efficient recombinant production are of pivotal interest in order to explore their intrinsic conformational dynamics and complex ligand binding behavior. We have systematically optimized the co-translational association and folding of G protein-coupled receptors with defined membranes of nanodiscs by cell-free expression approaches. Each optimization step was quantified and the ligand binding active fraction of the receptor samples could drastically be improved. The strategy was exemplified with a stabilized and a non-stabilized derivative of the turkey beta1-adrenergic receptor. Systematic lipid screens with preformed nanodiscs revealed that generation of ligand binding active conformations of the analyzed beta1-adrenergic receptors strongly depends on lipid charge, flexibility and chain length. The lipid composition of the nanodisc membranes modulates the affinities to a variety of ligands of both receptor derivatives. In addition, the thermostabilization procedure had a significant impact on specific ligand affinities of the receptor and abolished or reduced the binding of certain antagonists. Both receptors were highly stable after purification with optimized nanodisc membranes. The procedure avoids any detergent contact of the receptors and sample production takes less than two days. Moreover, even non-stabilized receptors can be analyzed and their prior purification is not necessary for the formation of nanodisc complexes. The established process appears therefore to be suitable as a new platform for the functional or even structural characterization of recombinant G protein-coupled receptors associated with defined lipid environments.

  1. Insights into the mechanism of interaction between trehalose-conjugated beta-sheet breaker peptides and Aβ(1-42) fibrils by molecular dynamics simulations.

    PubMed

    Autiero, Ida; Langella, Emma; Saviano, Michele

    2013-11-01

    An attractive strategy to contrast the Alzheimer disease (AD) is represented by the development of β-sheet breaker peptides (BSB). β-sheet breakers constitute a class of compounds which have shown a good efficacy in preventing the Aβ fibrillogenesis; however, their mechanism of action has not been precisely understood. In this context, we have studied the structural basis underlying the inhibitory effect of Aβ(1-42) fibrillogenesis explicated by two promising trehalose-conjugated BSB peptides using an all-atom molecular dynamics (MD) approach. Our simulations suggest that the binding on the two protofibril ends occurs through different binding modes. In particular, binding on the odd edge (chain A) is guided by a well defined hydrophobic cleft, which is common to both ligands. Moreover, targeting chain A entails a significant structure destabilization leading to a partial loss of β structure and is an energetically favoured process. A significant contribution of the trehalose moiety to the stability of the complexes emerged from our results. The energetically favoured hydrophobic cleft detected on chain A could represent a good starting point for the design of new molecules with improved anti-aggregating features.

  2. TGF-{beta} signals the formation of a unique NF1/Smad4-dependent transcription repressor-complex in human diploid fibroblasts

    SciTech Connect

    Luciakova, Katarina; Kollarovic, Gabriel; Kretova, Miroslava; Sabova, Ludmila; Nelson, B. Dean

    2011-08-05

    Highlights: {yields} TGF-{beta} induces the formation of unique nuclear NF1/Smad4 complexes that repress expression of the ANT-2 gene. {yields} Repression is mediated through an NF1-dependent repressor element in the promoter. {yields} The formation of NF1/Smad4 complexes and the repression of ANT2 are prevented by inhibitors of p38 kinase and TGF-{beta} RI. {yields} NF1/Smad complexes implicate novel role for NF1 and Smad proteins in the regulation of growth. -- Abstract: We earlier reported the formation of a unique nuclear NF1/Smad complex in serum-restricted fibroblasts that acts as an NF1-dependent repressor of the human adenine nucleotide translocase-2 gene (ANT2) [K. Luciakova, G. Kollarovic, P. Barath, B.D. Nelson, Growth-dependent repression of human adenine nucleotide translocator-2 (ANT2) transcription: evidence for the participation of Smad and Sp family proteins in the NF1-dependent repressor complex, Biochem. J. 412 (2008) 123-130]. In the present study, we show that TGF-{beta}, like serum-restriction: (a) induces the formation of NF1/Smad repressor complexes, (b) increases binding of the complexes to the repressor elements (Go elements) in the ANT2 promoter, and (c) inhibits ANT2 expression. Repression of ANT2 by TGF-{beta} is eliminated by mutating the NF1 binding sites in the Go repressor elements. All of the above responses to TGF-{beta} are prevented by inhibitors of TGF-{beta} RI and MAPK p38. These inhibitors also prevent NF1/Smad4 repressor complex formation and repression of ANT2 expression in serum-restricted cells, suggesting that similar signaling pathways are initiated by TGF-{beta} and serum-restriction. The present finding that NF1/Smad4 repressor complexes are formed through TGF-{beta} signaling pathways suggests a new, but much broader, role for these complexes in the initiation or maintenance of the growth-inhibited state.

  3. Critical roles of the TGF-beta type I receptor ALK5 in perichondrial formation and function, cartilage integrity, and osteoblast differentiation during growth plate development.

    PubMed

    Matsunobu, Tomoya; Torigoe, Kiyoyuki; Ishikawa, Masaki; de Vega, Susana; Kulkarni, Ashok B; Iwamoto, Yukihide; Yamada, Yoshihiko

    2009-08-15

    TGF-beta has been implicated in the proliferation and differentiation of chondrocytes and osteoblasts. However, the in vivo function of TGF-beta in skeletal development is unclear. In this study, we investigated the role of TGF-beta signaling in growth plate development by creating mice with a conditional knockout of the TGF-beta type I receptor ALK5 (ALK5(CKO)) in skeletal progenitor cells using Dermo1-Cre mice. ALK5(CKO) mice had short and wide long bones, reduced bone collars, and trabecular bones. In ALK5(CKO) growth plates, chondrocytes proliferated and differentiated, but ectopic cartilaginous tissues protruded into the perichondrium. In normal growth plates, ALK5 protein was strongly expressed in perichondrial progenitor cells for osteoblasts, and in a thin chondrocyte layer located adjacent to the perichondrium in the peripheral cartilage. ALK5(CKO) growth plates had an abnormally thin perichondrial cell layer and reduced proliferation and differentiation of osteoblasts. These defects in the perichondrium likely caused the short bones and ectopic cartilaginous protrusions. Using tamoxifen-inducible Cre-ER-mediated ALK5-deficient primary calvarial cell cultures, we found that TGF-beta signaling promoted osteoprogenitor proliferation, early differentiation, and commitment to the osteoblastic lineage through the selective MAPKs and Smad2/3 pathways. These results demonstrate the important roles of TGF-beta signaling in perichondrium formation and differentiation, as well as in growth plate integrity during skeletal development.

  4. Influence of osteogenic protein-1 (OP-1;BMP-7) and transforming growth factor-beta 1 on bone formation in vitro.

    PubMed

    Cheifetz, S; Li, I W; McCulloch, C A; Sampath, K; Sodek, J

    1996-01-01

    The bone morphogenetic proteins (BMPs) and transforming growth factor-beta s (TGF-beta s), are a group of structurally related proteins which have been shown to stimulate bone formation in vivo. Since these proteins are concentrated in the organic matrix of bone and would be released during bone resorption, they are likely to have a profound effect on the remodeling bone and may provide a link between bone resorption and bone formation. We are using primary cultures of fetal rat calvarial cells (FRCC) to study the independent and combined effects of OP-1/BMP-7 and TGF-beta 1 on bone cells at different stages of differentiation in order to identify responding cell populations and target genes. We have confirmed prior reports that OP-1 stimulates, while TGF-beta 1 inhibits, osteogenic differentiation in this system. The increase in both number and size of the mineralized nodules induced by OP-1 was accompanied by increased expression of alkaline phosphatase and type I collagen with an induction of bone sialoprotein (BSP) suggesting that OP-1 stimulates both differentiation and clonal expansion of osteoblastic cells. Interestingly, TGF-beta 1 abrogated OP-1 induced nodule formation. Despite these opposing effects on osteogenic differentiation, TGF-beta 1 (Wrana et al, 1991) and OP-1 both stimulated a rapid induction of osteopontin (OPN) mRNA in confluent FRCC cultures enriched in pre-osteoblastic cells. In contrast, when OP-1 was added to nodule-forming cultures which are enriched in osteoblastic cells, there was only a weak induction of OPN. Moreover, while the expression of one marker for mature osteoblasts (BSP) was refractory to OP-1, another (osteocalcin) was markedly stimulated. Thus OP-1 has selective effects on bone matrix protein expression that are dependent on the differentiated state of the cells.

  5. Quantitative analysis of co-oligomer formation by amyloid-beta peptide isoforms

    NASA Astrophysics Data System (ADS)

    Iljina, Marija; Garcia, Gonzalo A.; Dear, Alexander J.; Flint, Jennie; Narayan, Priyanka; Michaels, Thomas C. T.; Dobson, Christopher M.; Frenkel, Daan; Knowles, Tuomas P. J.; Klenerman, David

    2016-06-01

    Multiple isoforms of aggregation-prone proteins are present under physiological conditions and have the propensity to assemble into co-oligomers with different properties from self-oligomers, but this process has not been quantitatively studied to date. We have investigated the amyloid-β (Aβ) peptide, associated with Alzheimer’s disease, and the aggregation of its two major isoforms, Aβ40 and Aβ42, using a statistical mechanical modelling approach in combination with in vitro single-molecule fluorescence measurements. We find that at low concentrations of Aβ, corresponding to its physiological abundance, there is little free energy penalty in forming co-oligomers, suggesting that the formation of both self-oligomers and co-oligomers is possible under these conditions. Our model is used to predict the oligomer concentration and size at physiological concentrations of Aβ and suggests the mechanisms by which the ratio of Aβ42 to Aβ40 can affect cell toxicity. An increased ratio of Aβ42 to Aβ40 raises the fraction of oligomers containing Aβ42, which can increase the hydrophobicity of the oligomers and thus promote deleterious binding to the cell membrane and increase neuronal damage. Our results suggest that co-oligomers are a common form of aggregate when Aβ isoforms are present in solution and may potentially play a significant role in Alzheimer’s disease.

  6. Beta-hexosaminidase activity of the oral pathogen Tannerella forsythia influences biofilm formation on glycoprotein substrates.

    PubMed

    Roy, Sumita; Phansopa, Chatchawal; Stafford, Prachi; Honma, Kiyonobu; Douglas, C W Ian; Sharma, Ashu; Stafford, Graham P

    2012-06-01

    Tannerella forsythia is an important pathogen in periodontal disease. Previously, we showed that its sialidase activity is key to utilization of sialic acid from a range of human glycoproteins for biofilm growth and initial adhesion. Removal of terminal sialic acid residues often exposes β-linked glucosamine or galactosamine, which may also be important adhesive molecules. In turn, these residues are often removed by a group of enzymes known as β-hexosaminidases. We show here that T. forsythia has the ability to cleave glucosamine and galactosamine from model substrates and that this activity can be inhibited by the hexosaminidase inhibitor PugNAc (O-(2-acetamido-2-deoxy-d-glucopyranosylidene)amino N-phenyl carbamate). We now demonstrate for the first time that β-hexosaminidase activity plays a role in biofilm growth on glycoprotein-coated surfaces because biofilm growth and initial cell adhesion are inhibited by PugNAc. In contrast, adhesion to siallo-glycoprotein-coated surfaces is unaltered by PugNAc in the absence of sialidase activity (using a sialidase-deficient mutant) or surprisingly on the clinically relevant substrates saliva or serum. These data indicate that β-hexosaminidase activity has a significant role in biofilm formation in combination with sialidase activity in the biofilm lifestyle of T. forsythia.

  7. Stimulation of L-asparate beta-decarboxylase formation by L-glutamate in Pseudomonas dacunhae and Improved production of L-alanine.

    PubMed

    Shibatani, T; Kakimoto, T; Chibata, I

    1979-09-01

    The formation of L-asparate beta-decarboxylase by Pseudomonas dacunhae was compared on media containing a variety of organic acids and amino acids as a carbon source. Although the enzyme was formed constitutively when the organism was grown on basal medium or on that containing tricarboxylic acid cycle intermediates, it was induced twofold by L-glutamate and repressed one-tenth by L-serine. L-Glutamine, L-proline, L-leucine, glycine, and L-threonine also showed induction effects lower than that of L-glutamate. L-Glutamate derepressed the serine effect. This glutamate effect was observed effect was observed with other microoganisms, e.g., Achromobacter pestifer and Achromobacter liquidum. Since the intermediates from L-glutamate metabolism had no effect, this induction effect was specific to L-glutamate. The formation of some glutamate-related enzymes was measured and is discussed in relation to the formation of L-asparate beta-decarboxylase. L-Asparate beta-decarboxylase was purified to an electrophoretically homogenous state from L-glutamate-grown cells of P. dacunhae, and some properties were compared with those of the enzyme from fumarate-grown cells. The two enzymes were identical in disc electrophoresis, molecular weight, and some enzymatic properties. The industrial production of L-alanine from L-aspartic acid acid was improved by using the culture broth with highly induced L-asparate beta-decarboxylase (9.4 U/ml of broth).

  8. Formation of [b3 - 1 + cat]+ ions from metal-cationized tetrapeptides containing beta-alanine, gamma-aminobutyric acid or epsilon-aminocaproic acid residues.

    PubMed

    Osburn, Sandra M; Ochola, Sila O; Talaty, Erach R; Van Stipdonk, Michael J

    2008-11-01

    The presence and position of a single beta-alanine (betaA), gamma-aminobutyric acid (gammaABu) or epsilon-aminocaproic acid (Cap) residue has been shown to have a significant influence on the formation of b(n)+ and y(n)+ product ions from a series of model, protonated peptides. In this study, we examined the effect of the same residues on the formation of analogous [b3 - 1 + cat]+ products from metal (Li+, Na+ and Ag+)-cationized peptides. The larger amino acids suppress formation of b3+ from protonated peptides with general sequence AAXG (where X = beta-alanine, gamma-aminobutyric acid or epsilon-aminocaproic acid), presumably because of the prohibitive effect of larger cyclic intermediates in the 'oxazolone' pathway. However, abundant [b3 - 1 + cat]+ products are generated from metal-cationized versions of AAXG. Using a group of deuterium-labeled and exchanged peptides, we found that formation of [b3 - 1 + cat]+ involves transfer of either amide or alpha-carbon position H atoms, and the tendency to transfer the atom from the alpha-carbon position increases with the size of the amino acid in position X. To account for the transfer of the H atom, a mechanism involving formation of a ketene product as [b3 - 1 + cat]+ is proposed.

  9. Removal of the N-terminal hexapeptide from human beta2-microglobulin facilitates protein aggregation and fibril formation.

    PubMed Central

    Esposito, G.; Michelutti, R.; Verdone, G.; Viglino, P.; Hernández, H.; Robinson, C. V.; Amoresano, A.; Dal Piaz, F.; Monti, M.; Pucci, P.; Mangione, P.; Stoppini, M.; Merlini, G.; Ferri, G.; Bellotti, V.

    2000-01-01

    The solution structure and stability of N-terminally truncated beta2-microglobulin (deltaN6beta2-m), the major modification in ex vivo fibrils, have been investigated by a variety of biophysical techniques. The results show that deltaN6beta2-m has a free energy of stabilization that is reduced by 2.5 kcal/mol compared to the intact protein. Hydrogen exchange of a mixture of the truncated and full-length proteins at microM concentrations at pH 6.5 monitored by electrospray mass spectrometry reveals that deltaN6beta2-m is significantly less protected than its wild-type counterpart. Analysis of deltaN6beta2-m by NMR shows that this loss of protection occurs in beta strands I, III, and part of II. At mM concentration gel filtration analysis shows that deltaN6beta2-m forms a series of oligomers, including trimers and tetramers, and NMR analysis indicates that strand V is involved in intermolecular interactions that stabilize this association. The truncated species of beta2-microglobulin was found to have a higher tendency to self-associate than the intact molecule, and unlike wild-type protein, is able to form amyloid fibrils at physiological pH. Limited proteolysis experiments and analysis by mass spectrometry support the conformational modifications identified by NMR and suggest that deltaN6beta2-m could be a key intermediate of a proteolytic pathway of beta2-microglobulin. Overall, the data suggest that removal of the six residues from the N-terminus of beta2-microglobulin has a major effect on the stability of the overall fold. Part of the tertiary structure is preserved substantially by the disulfide bridge between Cys25 and Cys80, but the pairing between beta-strands far removed from this constrain is greatly perturbed. PMID:10850793

  10. Formation of. beta. ,. gamma. -methylene-7,8-dihydroneopterin 3'-triphosphate from. beta. ,. gamma. -methyleneguanosine 5'-triphosphate by GTP cyclohydrolase I of Escherichia coli

    SciTech Connect

    Ferre, J.; Jacobson, K.B.

    1984-01-01

    GTP cyclohydrolase I of Escherichia coli converts (..beta..,..gamma..-methylene)GTP to a fluorescent product that is characterized as (..beta..,..gamma..-methylene)dihydroneopterin triphosphate. Interaction between the GTP analog and the enzyme gave a K/sub i/ of 3.0 ..mu..M, which may be compared to the K/sub m/ of 0.1 ..mu..M for GTP. This new analog of dihydroneopterin triphosphate may, in turn, be converted to the same greenish-yellow pteridines (compounds X, X1, and X2) that are obtained from dihydroneopterin triphosphate. Because of its stability to phosphatase action, this analog may be useful for studies in pteridine metabolism. 14 references, 5 figures.

  11. Till formation under a soft-bedded palaeo-ice stream of the Scandinavian Ice Sheet, constrained using qualitative and quantitative microstructural analyses

    NASA Astrophysics Data System (ADS)

    Narloch, Włodzimierz; Piotrowski, Jan A.; Wysota, Wojciech; Tylmann, Karol

    2015-08-01

    This study combines micro- and macroscale studies, laboratory experiments and quantitative analyses to decipher processes of till formation under a palaeo-ice stream and the nature of subglacial sediment deformation. Till micromorphology (grain lineations, grain stacks, turbate structures, crushed grains, intraclasts and domains), grain-size and till fabric data are used to investigate a basal till generated by the Vistula Ice Stream of the Scandinavian Ice Sheet during the last glaciation in north-central Poland. A comparison of microstructures from the in situ basal till and laboratory-sheared till experiments show statistical relationships between the number of grain lineations and grain stacks; and between the number of grain lineations and turbate structures. Microstructures in the in situ till document both brittle and ductile styles of deformation, possibly due to fluctuating basal water pressures beneath the ice stream. No systematic vertical and lateral trends are detected in the parameters investigated in the in situ till, which suggests a subglacial mosaic of relatively stable and unstable areas. This situation can be explained by an unscaled space-transgressive model of subglacial till formation whereby at any given point in time different processes operated in different places under the ice sheet, possibly related to the distance from the ice margin and water pressure at the ice-bed interface. A new quantitative measure reflecting the relationship between the number of grain lineations and grain stacks may be helpful in discriminating between pervasive and non-pervasive deformation and constraining the degree of stress heterogeneity within a deformed bed. Independent strain magnitude estimations revealed by a quantitative analysis of micro- and macro-particle data show low cumulative strain in the ice-stream till in the order of 10-102.

  12. Soluble penicillin-binding protein 2a: beta-lactam binding and inhibition by non-beta-lactams using a 96-well format.

    PubMed

    Toney, J H; Hammond, G G; Leiting, B; Pryor, K D; Wu, J K; Cuca, G C; Pompliano, D L

    1998-01-01

    High level methicillin resistance in Staphylococcus aureus is dependent upon the acquisition of the mecA gene encoding penicillin-binding protein 2a (PBP2a). PBP2a is a member of a family of peptidoglycan biosynthetic enzymes involved in assembly of the cell wall in bacteria and is poorly inactivated by beta-lactam antibiotics. We describe a 96-well-filter binding assay using recombinant, soluble PBP2a which allows for kinetic measurement of penicillin binding. The deacylation rate constant for the PBP2a-penicillin G covalent complex was found to be 5.7 +/- 1.0 x 10(-5) s-1 at 30 degrees C (half-life of approximately 200 min). For the PBP2a acylation reaction, the value of K(m) (penicillin G) = 0.5 +/- 0.1 mM and kcat = 1 x 10(-3) s-1, which yields a second-order rate constant (kcat/K(m)) for inactivation of 2.0 M-1 s-1. Using this assay, several non-beta-lactam inhibitors including Cibacron blue have been found which exhibit IC50 values between 10 and 30 microM. The binding affinities of several carbapenems and beta-lactams correlated well between the filter binding assay described in this report and an electrophoretic assay for PBP2a using membranes prepared form methicillin-resistant S. aureus.

  13. Fibril stability in solutions of twisted Format="TEX"/>-sheet peptides: a new kind of micellization in chiral systems

    NASA Astrophysics Data System (ADS)

    Nyrkova, I. A.; Semenov, A. N.; Aggeli, A.; Boden, N.

    2000-10-01

    The problem of fibril (fibre) formation in chiral systems is explored theoretically being supported by experiments on synthetic de novo 11-mer peptide forming self-assembled -sheet tapes. Experimental data unambiguously indicate that the tapes form fibrils of nearly monodisperse thickness ca. 8-10 nm. Fibril formation and stabilisation are attributed to inter-tape face-to-face attraction and their intrinsic twist, correspondingly. The proposed theory is capable of predicting the fibril aggregation number and its equilibrium twist in terms of molecular parameters of the primary tapes. The suggested novel mechanism of twist stabilisation of finite aggregates (fibrils) is different to the well-known stabilisation of micelles in amphiphilic systems, and it is likely to explain the formation and stability of fibrils in a wide variety of systems including proteinaceous amyloid fibres, sickle-cell hemoglobin fibres responsible for HbS anemia, corkscrew threads found in chromonics in the presence of chiral additives and native cellulose microfibrillar crystallites. The theory also makes it possible to extract the basic molecular parameters of primary tapes (inter-tape attraction energy, helical twist step, elastic moduli) from the experimental data.

  14. Formation of varanic acid, 3 alpha, 7 alpha, 12 alpha, 24-tetrahydroxy-5 beta-cholestanoic acid from 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholestanoic acid in Bombina orientalis.

    PubMed

    Une, M; Inoue, A; Hoshita, T

    1996-11-01

    Varanic acid (3 alpha, 7 alpha, 12 alpha, 24-tetrahydroxy-5 beta-cholestanoic acid; 24-OH-THCA) is almost the sole component of bile acids in the bile of Bombina orientalis. To examine in the mechanism of the formation of 24-OH-THCA, radiolabeled (25R)- and (25S)-3 alpha, 7 alpha, 12 alpha-trihdroxy-5 beta-cholestanoic acids [(25R)- and (25S)-THCA] and (24E)-3 alpha, 7 alpha, 12 alpha-trihdroxy-5 beta-cholest-24-enoic acid (delta 24-THCA) were administered intraperitoneally to B. orientalis, gallbladder bile was collected after 24 h, and bile acids were subsequently extracted. Then the bile acids were analyzed by means of radio thin-layer chromatography and radio high-performance liquid chromatography after conversion to p-bromophenacyl ester derivatives. Although delta 24-THCA was not converted to 24-OH-THCA, (25R)-THCA and (25S)-THCA were transformed to (24R,25R)-24-OH-THCA and (24R,25S)-24-OH-THCA, respectively. These results strongly suggest that 24-OH-THCA was transformed via direct hydroxylation of the saturated side chain of THCA, not via hydration to an alpha, beta-unsaturated acid, delta 24-THCA, in B. orientalis.

  15. An RGD spacing of 440 nm is sufficient for integrin alpha V beta 3- mediated fibroblast spreading and 140 nm for focal contact and stress fiber formation

    PubMed Central

    1991-01-01

    The synthetic peptide Gly-Arg-Gly-Asp-Tyr (GRGDY), which contains the RGD sequence of several adhesion molecules, was covalently grafted to the surface of otherwise poorly adhesive glass substrates and was used to determine the minimal number of ligand-receptor interactions required for complete spreading of human foreskin fibroblasts. Well- defined adhesion substrates were prepared with GRGDY between 10(-3) fmol/cm2 and 10(4) fmol/cm2. As the adhesion ligand surface concentration was varied, several distinct morphologies of adherent cells were observed and categorized. The population of fully spread cells at 4 h reached a maximum at 1 fmol/cm2, with no further increases up to 10(4) fmol/cm2. Although maximal cell spreading was obtained at 1 fmol/cm2, focal contacts and stress fibers failed to form at RGD surface concentrations below 10 fmol/cm2. The minimal peptide spacings obtained in this work correspond to 440 nm for spreading and 140 nm for focal contact formation, and are much larger than those reported in previous studies with adsorbed adhesion proteins, adsorbed RGD-albumin conjugates, or peptide-grafted polyacrylamide gels. Vitronectin receptor antiserum specific for integrin alpha V beta 3 blocked cell adhesion and spreading on substrates containing 100 fmol/cm2 of surface- bound GRGDY, while fibronectin receptor antiserum specific for alpha 5 beta 1 did not. Furthermore, alpha V beta 3 was observed to cluster into focal contacts in spread cells, but alpha 5 beta 1 did not. It was thus concluded that a peptide-to-peptide spacing of 440 nm was required for alpha V beta 3-mediated cellular spreading, while 140 nm was required for alpha V beta 3-mediated focal contact formation and normal stress fiber organization in human foreskin fibroblasts; these spacings represent much fewer ligands than were previously thought to be required. PMID:1714913

  16. 9-Fluorenylmethoxycarbonyl (Fmoc)-glycine coupling of saccharide beta-glycosylamines for the fractionation of oligosaccharides and the formation of neoglycoconjugates.

    PubMed

    Arsequell, G; Dwek, R A; Wong, S Y

    1994-01-01

    We have devised a new saccharide derivatization scheme to provide not only the temporary attachment of a chromophore for detecting and facilitating the chromatographic separation of carbohydrates, but also the intermediates for further derivatization to produce neoglycoconjugates. Several neutral unprotected saccharide beta-glycosylamines were formed by the direct condensation of the reducing saccharides with aqueous ammonium bicarbonate. The beta-glycosylamine derivatives of N-acetylglucosamine, di-N-acetylchitobiose, and asialo-, digalactosylated biantennary complex oligosaccharide were N-acylated separately with excess 9-fluorenylmethoxycarbonyl (Fmoc)-glycine. The Fmoc-glycinamido beta-derivatives of these unprotected saccharides were well separated by normal-phase high-performance liquid chromatography and detected by ultraviolet absorption. Similar derivatization and fractionation of a partial acid hydrolyzate of chitin were equally successful resulting in the separation of Fmoc-glycinamido derivatives of di-N-acetylchitobiose to hepta-N-acetylchitoheptaose in the hydrolyzate. The reversibility of the Fmoc derivatization was demonstrated by treating the Fmoc-glycinamido derivative of N-acetylglucosamine with piperidine to generate its 1-N-glycyl-beta-saccharide derivative. The structure and stereochemistry of this product was confirmed by proton nuclear magnetic resonance spectroscopy. The 1-N-glycyl-beta-saccharide derivatives are stable intermediates for the formation of asparagine-linked neoglycoconjugates.

  17. [Beta]-Adrenergic Receptors in the Insular Cortex are Differentially Involved in Aversive vs. Incidental Context Memory Formation

    ERIC Educational Resources Information Center

    Miranda, Maria Isabel; Sabath, Elizabeth; Nunez-Jaramillo, Luis; Puron-Sierra, Liliana

    2011-01-01

    The goal of this research was to determine the effects of [beta]-adrenergic antagonism in the IC before or after inhibitory avoidance (IA) training or context pre-exposure in a latent inhibition protocol. Pretraining intra-IC infusion of the [beta]-adrenergic antagonist propranolol disrupted subsequent IA retention and impaired latent inhibition…

  18. Late Noachian and early Hesperian ridge systems in the south circumpolar Dorsa Argentea Formation, Mars: Evidence for two stages of melting of an extensive late Noachian ice sheet

    NASA Astrophysics Data System (ADS)

    Kress, Ailish M.; Head, James W.

    2015-05-01

    The Dorsa Argentea Formation (DAF), extending from 270°-100° E and 70°-90° S, is a huge circumpolar deposit surrounding and underlying the Late Amazonian South Polar Layered Deposits (SPLD) of Mars. Currently mapped as Early-Late Hesperian in age, the Dorsa Argentea Formation has been interpreted as volatile-rich, possibly representing the remnants of an ancient polar ice cap. Uncertain are its age (due to the possibility of poor crater retention in ice-related deposits), its mode of origin, the origin of the distinctive sinuous ridges and cavi that characterize the unit, and its significance in the climate history of Mars. In order to assess the age of activity associated with the DAF, we examined the ridge populations within the Dorsa Argentea Formation, mapping and characterizing seven different ridge systems (composed of nearly 4,000 ridges covering a total area of ~300,000 km2, with a cumulative length of ridges of ~51,000 km) and performing crater counts on them using the method of buffered crater counting to determine crater retention ages of the ridge populations. We examined the major characteristics of the ridge systems and found that the majority of them were consistent with an origin as eskers, sediment-filled subglacial drainage channels. Ridge morphologies reflect both distributed and channelized esker systems, and evidence is also seen that some ridges form looping moraine-like termini distal to some distributed systems. The ridge populations fall into two age groups: ridge systems between 270° and 0° E date to the Early Hesperian, but to the east, the Promethei Planum and the Chasmata ridge systems date to the Late Noachian. Thus, these ages, and esker and moraine-like morphologies, support the interpretation that the DAF is a remnant ice sheet deposit, and that the esker systems represent evidence of significant melting and drainage of meltwater from portions of this ice sheet, thus indicating at least some regions and/or periods of wet

  19. Double Mantle Plume Upwelling—A Possible Formation Mechanism of Beta Plateau and Devana Chasma,Venus

    NASA Astrophysics Data System (ADS)

    Ding, N.

    2009-12-01

    Ning Ding,Zuoxun Zeng,China University of Geosciences,Wuhan,430074,China NingDing.eagle@gmail.com Introduction:Venus represents a‘one plate planet’[1],and the uplift,fractures and volcanism in Beta Regio on Venus are considered to be formed by lithosphere uplift driven by a hot plume[2]. Based on the double peaking saddle landform,we suggest the tectonic pattern of double mantle plume upwelling to interpret the formation mechanism of Beta Plateau and Devana Chasma.We take a physical modeling to validate this possibility. Model:There is no ductile shear in Venus[3],so we use quartz sands to simulate the crust of Venus.We use two wood stickes 1.5cm in diameter rising from the rubber canvas slowly and straight till about half of the model,then falling down slowly and straight.The base is a hard rubber plate,in the center of which,there are two holes 3cm in diameter,and the distance between them is 5cm.The holes are covered by rubber canvas.We use the quartz sands in colours of white, red and black with particle size of 70 mess as the model materials. Result:Fig.1:At the beginning of the wood stickes upwelling,only fine radial cracks are formed above the upwelling from central to outside.With the upwelling continue,surface energy of the fine radial cracks increase and make the cracks unstable,finally,the fine radial cracks connect each other and form a fracture zone.And then the two mantle plume downwelling,the fracture zone is developed to form a chasma at the end. Fig.2:The four profiles all form reverse faults outside and normal faults inside.But the difference is the faults in the middle of the chasma goes deeper than others.It is the pattern of Beta Plateau where the tectonic rising is cut by Devana Chasma zone in the topographic features. Fig.3:From the tow fig., we can see two points similar:a.the elevation is high and distribution area is large around the area of two upwelling and it is high around the area of chasma,but the distribution area is small

  20. Influence of Water Content on the β-Sheet Formation, Thermal Stability, Water Removal, and Mechanical Properties of Silk Materials.

    PubMed

    Yazawa, Kenjiro; Ishida, Kana; Masunaga, Hiroyasu; Hikima, Takaaki; Numata, Keiji

    2016-03-14

    Silk, which has excellent mechanical toughness and is lightweight, is used as a structural material in nature, for example, in silkworm cocoons and spider draglines. However, the industrial use of silk as a structural material has garnered little attention. For silk to be used as a structural material, its thermal processability and associated properties must be well understood. Although water molecules influence the glass transition of silk, the effects of water content on the other thermal properties of silks are not well understood. In this study, we prepared Bombyx mori cocoon raw fibers, degummed fibers, and films with different water contents and then investigated the effects of water content on crystallization, degradation, and water removal during thermal processing. Thermal gravimetric analyses of the silk materials showed that water content did not affect the thermal degradation temperature but did influence the water removal behavior. By increasing the water content of silk, the water molecules were removed at lower temperatures, indicating that the amount of free water in silk materials increased; additionally, the glass transition temperature decreased with increasing water plasticization. Differential scanning calorimetry and wide-angle X-ray scattering of the silk films also suggested that the water molecules in the amorphous regions of the silk films acted as a plasticizer and induced β-sheet crystallization. The plasticizing effect of water was not detected in silk fibers, owing to their lower amorphous content and mobility. The structural and mechanical characterizations of the silk films demonstrated the silk film prepared at RH 97% realized both crystallinity and ductility simultaneously. Thus, the thermal stability, mechanical, and other properties of silk materials are regulated by their water content and crystallinity.

  1. The geometry of alpha-sheet: Implications for its possible function as amyloid precursor in proteins.

    PubMed

    Hayward, Steven; Milner-White, E James

    2008-04-01

    alpha-sheet has been proposed as the main constituent of the prefibrillar intermediate during amyloid formation. Here the helical parameters of the alpha-sheet strand are calculated from average main-chain dihedral angles reported from molecular dynamics simulations. It is an almost linear polypeptide that forms a right-handed helix of about 100 A diameter, with 100 residues and a rise of 30 A per turn. The strands are curved but untwisted, which implies that neighboring strands need not coil to make interstrand hydrogen bonds. This suggests that compared to beta-sheets in native folded proteins, alpha-sheets can be larger and stack more easily to create extensive 3D blocks. It is shown that alpha-sheet is related to a category of structures termed "mirror" structures. Mirror structures have repetitive pairs of main-chain dihedral angles at residues i and i+1 that satisfy the condition phi(i) (+1) = -psi(i), psi(i) (+1) = -phi(i). They are uniquely identified by the two orientations of their peptide planes, specified by phi(i) and psi(i). Their side chains point alternately in opposite directions. Interestingly, their conformations are insensitive to phi(i) and psi(i) in that the pseudo dihedral angle formed by four consecutive C(alpha) atoms is always close to 180 degrees . There are two types: "beta-mirror" and "alpha-mirror" structure; beta-mirror structures relate to beta-sheet by small peptide plane rotations, of less than 90 degrees , while alpha-mirror structures are close to alpha-sheet and relate to beta-sheet by approximately 180 degrees peptide plane flips. Most mirror structures, and in particular the alpha-mirror, form wide helices with diameters 50-70 A. Their gentle curvature, and therefore that of the alpha-sheet, arises from the orientation of successive peptide units causing the difference in the bond angles at the C and N atoms of the peptide unit to gradually change the direction of the chain.

  2. Effect of dietary. beta. -carotene, vitamin A and selenium on formation of preneoplastic lesions in rat liver

    SciTech Connect

    Colford, J.; Parker, R.S.

    1986-03-05

    The effect of dietary ..beta..-carotene (BC), retinyl acetate (RA) and sodium selenite on formation of ..gamma..-glutamyltranspeptidase-positive foci in rat liver was investigated. Male Sprague-Dawley rats, 50g, were fed for 16 wks semipurified diets supplemented with either BC (500 mg/kg diet), RA (6400 IU/kg diet for wks 1-7 and 10,000 IU/kg for wks 8-16), 1.8 ppm selenium (Se) or both 1.8 ppm Se and 500 mg/kg BC. The control diet contained 0.1 ppm Se and 3200 IU RA/kg diet. During wks 3-4 rats received 10 intragastric doses of aflatoxin B/sub 1/ (0.4 mg/kg body weight/dose). Preneoplastic foci were quantitated at wk 16. Diet had no significant effect on growth rate or food consumption. None of the treatments resulted in significant differences in the number of foci per cm/sup 2/ liver section, but differences in focal size occurred. RA increased total focal area (mm/sup 2//cm/sup 2/ liver), while Se decreased focal area 5-fold. BC slightly decreased focal area. The combination of BC and Se was not as effective as Se alone. BC, RA, and BC-Se diets yielded equivalent levels of total liver retinol, which exceeded levels in control and Se rats by 30-fold. Livers from BC fed rats contained 4-5 ..mu..g BC/g liver. The different effects of dietary RA and BC on focal development may indicate a role for BC other than as a retinol precursor. The influence of each nutrient on focal size, but not number, implies they act during the post-initiation stage of focal development.

  3. Efficient triple helix formation by oligodeoxyribonucleotides containing alpha- or beta-2-amino-5-(2-deoxy-D-ribofuranosyl) pyridine residues.

    PubMed Central

    Bates, P J; Laughton, C A; Jenkins, T C; Capaldi, D C; Roselt, P D; Reese, C B; Neidle, S

    1996-01-01

    Triple helices containing C+xGxC triplets are destabilised at physiological pH due to the requirement for base protonation of 2'-deoxycytidine (dC), which has a pKa of 4.3. The C nucleoside 2-amino-5-(2'-deoxy-beta-D-ribofuranosyl)pyridine (beta-AP) is structurally analogous to dC but is considerably more basic, with a pKa of 5.93. We have synthesised 5'-psoralen linked oligodeoxyribonucleotides (ODNs) containing thymidine (dT) and either beta-AP or its alpha-anomer (alpha-AP) and have assessed their ability to form triplexes with a double-stranded target derived from standard deoxynucleotides (i.e. beta-anomers). Third strand ODNs derived from dT and beta-AP were found to have considerably higher binding affinities for the target than the corresponding ODNs derived from dT and either dC or 5-methyl-2'-deoxycytidine (5-Me-dC). ODNs containing dT and alpha-AP also showed enhanced triplex formation with the duplex target and, in addition are more stable in serum-containing medium than standard oligopyrimidine-derived ODNs or ODNs derived from dT and beta-AP. Molecular modelling studies showed that an alpha-anomeric AP nucleotide can be accommodated within an otherwise beta-anomeric triplex with only minor perturbation of the triplex structure. Molecular dynamics (MD) simulations on triplexes containing either the alpha- or beta-anomer of (N1-protonated) AP showed that in both cases the base retained two standard hydrogen bonds to its associated guanine when the 'A-type' model of the triplex was used as the start-point for the simulation, but that bifurcated hydrogen bonds resulted when the alternative 'B-type' triplex model was used. The lack of a differential stability between alpha-AP- and beta-AP-containing triplexes at pH >7, predicted from the behaviour of the B-type models, suggests that the A-type models are more appropriate. PMID:8932369

  4. The evidence for the role of transforming growth factor-beta in the formation of abnormal scarring.

    PubMed

    Chalmers, Richard L

    2011-06-01

    The complex biological and physiological mechanisms that result in poor quality scarring are still not fully understood. This review looks at current evidence of the role of transforming growth factor-beta (TGFβ) in this pathological process.

  5. The thioesterase Bhp is involved in the formation of beta-hydroxytyrosine during balhimycin biosynthesis in Amycolatopsis balhimycina.

    PubMed

    Mulyani, Sri; Egel, Ellen; Kittel, Claudia; Turkanovic, Suada; Wohlleben, Wolfgang; Süssmuth, Roderich D; van Pée, Karl-Heinz

    2010-01-25

    The putative hydrolase gene bhp from the balhimycin biosynthetic gene cluster has been cloned and overexpressed in Escherichia coli. The corresponding enzyme Bhp was purified to homogeneity by nickel-chelating chromatography and characterized. Although Bhp has sequence similarities to hydrolases with "haloperoxidase"/perhydrolase activity, it did not show any enzymatic activity with standard "haloperoxidase"/perhydrolase substrates (e.g., monochlorodimedone and phenol red), nonspecific esterase substrates (such as p-nitrophenyl acetate, p-nitrophenyl phosphate and S-thiophenyl acetate) or the model lactonase substrate dihydrocoumarin. However, Bhp could be shown to catalyse the hydrolysis of S-beta-hydroxytyrosyl-N-acetyl cysteamine thioester (beta-OH-Tyr-SNAC) with 15 times the efficiency of S-L-tyrosyl-N-acetyl cysteamine thioester (L-Tyr-SNAC). This is in agreement with the suggestion that Bhp is involved in balhimycin biosynthesis, during which it was supposed to catalyse the hydrolysis of beta-OH-Tyr-S-PCP (PCP=peptidyl carrier protein) to free beta-hydroxytyrosine (beta-OH-Tyr) and strongly suggests that Bhp is a thioesterase with high substrate specificity for PCP-bound beta-OH-Tyr and not a "haloperoxidase"/perhydrolase or nonspecific esterase.

  6. The effect of glutamic acid side chain on acidity constant of lysine in beta-sheet: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Sargolzaei, M.; Afshar, M.; Sadeghi, M. S.; Kavee, M.

    2014-07-01

    In this work, the possibility of proton transfer between side chain of lysine and glutamic acid in peptide of Glu--Ala-Lys+ was demonstrated using density functional theory (DFT). We have shown that the proton transfer takes place between side chain of glutamic and lysine residues through the hydrogen bond formation. The structures of transition state for proton transfer reaction were detected in gas and solution phases. Our kinetic studies show that the proton transfer reaction rate in gas phase is higher than solution phase. The ionization constant (p K a) value of lysine residue in peptide was estimated 1.039 which is lower than intrinsic p K a of lysine amino acid.

  7. Splicing and 3' end formation in the definition of nonsense-mediated decay-competent human beta-globin mRNPs.

    PubMed

    Neu-Yilik, G; Gehring, N H; Thermann, R; Frede, U; Hentze, M W; Kulozik, A E

    2001-02-01

    Premature translation termination codons are common causes of genetic disorders. mRNAs with such mutations are degraded by a surveillance mechanism termed nonsense-mediated decay (NMD), which represents a phylogenetically widely conserved post-transcriptional mechanism for the quality control of gene expression. How NMD-competent mRNPs are formed and specified remains a central question. Here, we have used human beta-globin mRNA as a model system to address the role of splicing and polyadenylation for human NMD. We show that (i) splicing is an indispensable component of the human beta-globin NMD pathway, which cannot be compensated for by exonic beta-globin 'failsafe' sequences; (ii) the spatial requirements of human beta-globin NMD, as signified by the maximal distance of the nonsense mutation to the final exon-exon junction, are less constrained than in yeast; and (iii) non-polyadenylated mRNAs with a histone 3' end are NMD competent. Thus, the formation of NMD-competent mRNP particles critically depends on splicing but does not require the presence of a poly(A) tail.

  8. Formation of {beta}-nickel hydroxide plate-like structures under mild conditions and their optical properties

    SciTech Connect

    Moura, A.P. de; Lima, R.C.; Paris, E.C.; Li, M.S.; Varela, J.A.; Longo, E.

    2011-10-15

    Nanostructural {beta}-nickel hydroxide ({beta}-Ni(OH){sub 2}) plates were prepared using the microwave-hydrothermal (MH) method at a low temperature and short reaction times. An ammonia solution was employed as the coordinating agent, which reacts with [Ni(H{sub 2}O){sub 6}]{sup 2+} to control the growth of {beta}-Ni(OH){sub 2} nuclei. A trigonal {beta}-Ni(OH){sub 2} single phase was observed by X-ray diffraction (XRD) analyses, and the crystal cell was constructed with structural parameters and atomic coordinates obtained from Rietveld refinement. Field emission scanning electron microscopy (FE-SEM) images revealed that the samples consisted of hexagonal-shaped nanoplates with a different particle size distribution. Broad absorption bands assigned as transitions of Ni{sup 2+} in oxygen octahedral sites were revealed by UV-vis spectra. Photoluminescence (PL) properties observed with a maximum peak centered in the blue-green region were attributed to different defects, which were produced during the nucleation process. We present a growth process scheme of the {beta}-Ni(OH){sub 2} nanoplates. - Graphical abstract: Nanostructural {beta}-Ni(OH){sub 2} crystalline powders were prepared by rapid microwave-hydrothermal method for 1, 8 and 32 min. The hexagonal-shaped nanoplates obtained presented PL emission in the blue-green region and each decomposed component represents a different type of electronic transition, which can be linked to the structural arrangement or surface defects. Highlights: > Ammonia solution to control the growth of {beta}-Ni(OH){sub 2} nuclei. > Regular plates-shape related to crystallization-dissolution-recrystallization. > The surface states and lattice defects generated in growth mechanism of crystals. > Different defects produced in the growth process responsible by photoluminescence. > Each component of photoluminescence curve linked to structural arrangement or surface defects.

  9. Structural studies of the N-terminal fragments of the WW domain: Insights into co-translational folding of a beta-sheet protein

    PubMed Central

    Hanazono, Yuya; Takeda, Kazuki; Miki, Kunio

    2016-01-01

    Nascent proteins fold co-translationally because the folding speed and folding pathways are limited by the rate of ribosome biosynthesis in the living cell. In addition, though full-length proteins can fold all their residues during the folding process, nascent proteins initially fold only with the N-terminal residues. However, the transient structure and the co-translational folding pathway are not well understood. Here we report the atomic structures of a series of N-terminal fragments of the WW domain with increasing amino acid length. Unexpectedly, the structures indicate that the intermediate-length fragments take helical conformations even though the full-length protein has no helical regions. The circular dichroism spectra and theoretical calculations also support the crystallographic results. This suggests that the short-range interactions are more decisive in the structure formation than the long-range interactions for short nascent proteins. In the course of the peptide extension, the helical structure change to the structure mediated by the long-range interactions at a particular polypeptide length. Our results will provide unique information for elucidating the nature of co-translational folding. PMID:27698466

  10. FORMATION OF BETA-HYDROXYCARBONYLS FROM THE OH RADICAL-INITIATED REACTIONS OF SELECTED ALKENES (R825252)

    EPA Science Inventory

    beta2.gif" BORDER=0 ALIGN="middle">-Hydroxycarbonyls can be formed from the gas-phase
    reactions of alkenes with the OH radical, both in the presence
    and in the absence of NO. To date, because of analytical
    difficulties, few data have been r...

  11. Synthesis of porous sheet-like Co{sub 3}O{sub 4} microstructure by precipitation method and its potential applications in the thermal decomposition of ammonium perchlorate

    SciTech Connect

    Lu Shanshan; Jing Xiaoyan; Liu Jingyuan; Wang Jun; Liu Qi; Zhao Yanhua; Jamil, Saba; Zhang Milin; Liu Lianhe

    2013-01-15

    Porous sheet-like cobalt oxide (Co{sub 3}O{sub 4}) were successfully synthesized by precipitation method combined with calcination of cobalt hydroxide precursors. The structure, morphology and porosity properties of the products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption-desorption measurement. The as-prepared sheet-like microstructures were approximately 2-3 {mu}m in average diameter, and the morphology of the cobalt hydroxide precursors was retained after the calcination process. However, it appeared a large number of uniform pores in the sheets after calcination. In order to calculate the potential catalytic activity, the thermal decomposition of ammonium perchlorate (AP) has been analyzed, in which cobalt oxide played a role of an additive and the porous sheet-like Co{sub 3}O{sub 4} microstructures exhibited high catalytic performance and considerable decrease in the thermal decomposition temperature of AP. Moreover, a formation mechanism for the sheet-like microstructures has been discussed. - Graphical abstract: Porous sheet-like Co{sub 3}O{sub 4} were synthesized by facile precipitation method combined with calcination of {beta}-Co(OH){sub 2} precursors. Thermogravimetric-differential scanning calorimetric analysis indicates potential catalytic activity in the thermal decomposition of ammonium perchlorate. Highlights: Black-Right-Pointing-Pointer Synthesis of sheet-like {beta}-Co(OH){sub 2} precursors by precipitation method. Black-Right-Pointing-Pointer Porous sheet-like Co{sub 3}O{sub 4} were obtained by calcining {beta}-Co(OH){sub 2} precursors. Black-Right-Pointing-Pointer The possible formation mechanism of porous sheet-like Co{sub 3}O{sub 4} has been discussed. Black-Right-Pointing-Pointer Porous sheet-like Co{sub 3}O{sub 4} decrease the thermal decomposition temperature of ammonium perchlorate.

  12. The prostaglandin receptor EP2 activates multiple signaling pathways and beta-arrestin1 complex formation during mouse skin papilloma development.

    PubMed

    Chun, Kyung-Soo; Lao, Huei-Chen; Trempus, Carol S; Okada, Manabu; Langenbach, Robert

    2009-09-01

    Prostaglandin E(2) (PGE(2)) is elevated in many tumor types, but PGE(2)'s contributions to tumor growth are largely unknown. To investigate PGE(2)'s roles, the contributions of one of its receptors, EP2, were studied using the mouse skin initiation/promotion model. Initial studies indicated that protein kinase A (PKA), epidermal growth factor receptor (EGFR) and several effectors-cyclic adenosine 3',5'-monophosphate response element-binding protein (CREB), H-Ras, Src, protein kinase B (AKT) and extracellular signal-regulated kinase (ERK)1/2-were activated in 12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted papillomas and that PKA and EGFR inhibition (H89 and AG1478, respectively) decreased papilloma formation. EP2's contributions to the activation of these pathways and papilloma development were determined by inhibiting endogenous TPA-induced PGE(2) production with indomethacin (Indo) and concomitantly treating with the EP2 agonist, CAY10399 (CAY). CAY treatment restored papilloma formation in TPA/Indo-treated mice and increased cyclic adenosine 3',5'-monophosphate and PKA activation as measured by p-CREB formation. CAY treatment also increased EGFR and Src activation and their inhibition by AG1478 and PP2 indicated that Src was upstream of EGFR. CAY also increased H-Ras, ERK1/2 and AKT activation, and AG1478 decreased their activation indicating EGFR being upstream. Supporting EP2's contribution, EP2-/- mice exhibited 65% fewer papillomas and reduced Src, EGFR, H-Ras, AKT and ERK1/2 activation. G protein-coupled receptor (GPCR) activation of EGFR has been reported to involve Src's activation via a GPCR-beta-arrestin-Src complex. Indeed, immunoprecipitation of beta-arrestin1 or p-Src indicated the presence of an EP2-beta-arrestin1-p-Src complex in papillomas. The data indicated that EP2 contributed to tumor formation via activation of PKA and EGFR and that EP2 formed a complex with beta-arrestin1 and Src that contributed to signaling and/or EP2 desensitization.

  13. Mechanism of formation of the C-terminal beta-hairpin of the B3 domain of the immunoglobulin binding protein G from Streptococcus. I. Importance of hydrophobic interactions in stabilization of beta-hairpin structure.

    PubMed

    Skwierawska, Agnieszka; Makowska, Joanna; Ołdziej, Stanisław; Liwo, Adam; Scheraga, Harold A

    2009-06-01

    We previously studied a 16-amino acid-residue fragment of the C-terminal beta-hairpin of the B3 domain (residues 46-61), [IG(46-61)] of the immunoglobulin binding protein G from Streptoccocus, and found that hydrophobic interactions and the turn region play an important role in stabilizing the structure. Based on these results, we carried out systematic structural studies of peptides derived from the sequence of IG (46-61) by systematically shortening the peptide by one residue at a time from both the C- and the N-terminus. To determine the structure and stability of two resulting 12- and 14-amino acid-residue peptides, IG(48-59) and IG(47-60), respectively, we carried out circular dichroism, NMR, and calorimetric studies of these peptides in pure water. Our results show that IG(48-59) possesses organized three-dimensional structure stabilized by hydrophobic interactions (Tyr50-Phe57 and Trp48-Val59) at T = 283 and 305 K. At T = 313 K, the structure breaks down because of increased chain entropy, but the turn region is preserved in the same position observed for the structure of the whole protein. The breakdown of structure occurs near the melting temperature of this peptide (T(m) = 310 K) measured by differential scanning calorimetry (DSC). The melting temperature of IG(47-60) determined by DSC is T(m) = 330 K and its structure is similar to that of the native beta-hairpin at all (lower) temperatures examined (283-313 K). Both of these truncated sequences are conserved in all known amino acid sequences of the B domains of the immunoglobulin binding protein G from bacteria. Thus, this study contributes to an understanding of the mechanism of folding of this whole family of proteins, and provides information about the mechanism of formation and stabilization of a beta-hairpin structural element.

  14. Induction of multinucleation by beta-glucosyl Yariv reagent in regenerated cells from Marchantia polymorpha protoplasts and involvement of arabinogalactan proteins in cell plate formation.

    PubMed

    Shibaya, Taeko; Sugawara, Yasutake

    2009-08-01

    Arabinogalactan proteins (AGPs) are abundant plant cell surface proteoglycans widely distributed in plant species. Since high concentrations of beta-glucosyl Yariv reagent (betaglcY), which binds selectively to AGPs, inhibited cell division of protoplast-regenerated cells of the liverwort Marchantia polymorpha L. (Shibaya and Sugawara in Physiol Plant 130:271-279, 2007), we investigated the mechanism underlying the inability of the cells to divide normally by staining nuclei, cell walls and beta-1,3-glucan. Microscopic observation showed that the diameter of regenerated cells cultured with betaglcY was about 2.8-fold larger than that of cells cultured without betaglcY. The cells cultured with betaglcY were remarkably multinucleated. These results indicated that betaglcY did not inhibit mitosis but induced multinucleation. In the regenerated cells cultured with low concentrations of betaglcY (5 and 1 microg ml(-1)), the cell plate was stained strongly by betaglcY, suggesting abundant AGPs in the forming cell plate. In these cell plates, beta-1,3-glucan was barely detectable or not detected. In multinucleated cells, cell plate-like fragments, which could not reach the cell wall, were frequently observed and they were also stained strongly by betaglcY. Our results indicated that AGPs might have an important role in cell plate formation, and perturbation of AGPs with betaglcY might result in remarkable multinucleation in protoplast-regenerated cells of M. polymorpha.

  15. TGF{beta}-mediated formation of pRb-E2F complexes in human myeloid leukemia cells

    SciTech Connect

    Hu Xiaotang

    2008-05-02

    TGF{beta} is well known for its inhibitory effect on cell cycle G1 checkpoint kinases. However, its role in the control of pRb-E2F complexes is not well established. TGF{beta} inhibits phosphorylation of pRb at several serine and threonine residues and regulates the association of E2F transcription factors with pRb family proteins. Recent studies found that predominantly E2F-4, p130, and histone deacetylase (HDAC) are found to bind to corresponding E2F-responsive promoters in G0/G1 phase. As cells progress through mid-G1, p130-E2F4 complex are replaced by p107-E2F4 followed by activators E2F1, 2, and 3. pRb was not detectable in the promoters containing the E2F-responsive site in cycling cells but was associated with E2F4-p130 complexes or E2F4-p107 complexes during G0/G1 phase. In human myeloid leukemia cell line, MV4-11, TGF{beta} upregulated pRb-E2F-4 and p130-E2F-4, and downregulated p107-E2F-4 complexes. However, pRB-E2F1 and pRb-E2F3 complexes were found in proliferating cells but not in TGF{beta} arrested G1 cells. In addition, electrophoretic gel mobility shift assay (EMSA) could not detect pRb-E2F DNA-binding activities either in S or G1 phase but exhibited the existence of p107-E2F4 in proliferating cells and p130-E2F4 complexes in TGF{beta}-arrested G1 cells, respectively. Our data suggest that p107 and p130, but not pRb, and the repressor E2F, but not activator E2Fs, play a critical role in regulating E2F-responsive gene expression in TGF{beta}-mediated cell cycle control in human myeloid leukemia cells.

  16. Study on the Formation and Characterization of the Intermetallics in Friction Stir Welding of Aluminum Alloy to Coated Steel Sheet Lap Joint

    NASA Astrophysics Data System (ADS)

    Das, H.; Ghosh, R. N.; Pal, T. K.

    2014-10-01

    Multimaterial fabrication such as joining of steel and aluminum is currently prominent in a variety of industries. Friction stir welding is a novel solid-state welding process that causes good joint strength between steel and aluminum. However, the phenomenon contributing significant strength at the interface is not yet clear. In the present study, the interface of the friction stir lap-welded aluminum and coated steel sheet having joint strength maximum (71.4 pct of steel base metal) and minimum, respectively, under two parameter combinations, i.e., 1000 rpm 50 mm min-1 and 500 rpm 100 mm min-1, was exclusively characterized by X-ray diffraction, transmission electron microscopy (TEM), concentration profile, and elemental mapping by electron-probe microanalysis. A TEM-assisted EDS study identifies the morphologies of large size Al13Fe4 and small size Fe3Al-type intermetallic compounds at the interface. The diffusion-induced intermetallic growth (thickness) measured from a backscattered image and concentration profile agreed well with the numerically calculated one. The growth of these two phases at 1000 rpm 50 mm min-1 is attributed to the slower cooling rate (~3.5 K/s) with higher diffusion time (44 seconds) along the interface in comparison to the same for 500 rpm 100 mm min-1 with faster cooling rate (~10 K/s) and less diffusion time (13.6 seconds). The formation of thermodynamically stable and hard intermetallic phase Al13Fe4 at 1000 rpm and travel speed 50 mm min-1 in amounts higher than 500 rpm and a travel speed of 100 mm min-1 results in better joint strength, i.e., 71.4 pct, of the steel base metal.

  17. Secondary structure characterization of beta-lactamase inclusion bodies.

    PubMed

    Przybycien, T M; Dunn, J P; Valax, P; Georgiou, G

    1994-01-01

    The secondary structure of proteins in E. coli inclusion bodies was investigated via Raman spectroscopy. Inclusion bodies were purified from cells expressing different forms of RTEM beta-lactamase and grown at either 37 or 42 degrees C. All of the solid phase inclusion body samples examined gave amide I band spectra that were perturbed from that of the native, purified protein in both solution and powder forms; secondary structure estimates indicated significant decreases in alpha-helix and increases in beta-sheet contents in the inclusion body samples. The structure estimates for inclusion bodies isolated from 37 degrees C cultures were similar, regardless of aggregate localization in the E. coli cytoplasmic or periplasmic spaces or beta-lactamase precursor content. Inclusion bodies obtained from 42 degrees C cells exhibited a further reduction of alpha-helix and augmentation of beta-sheet contents relative to those from 37 degrees C cultures. These results are consistent with the paradigm for inclusion body formation via the self-association of intra-cellular folding intermediates having extensive secondary structure content. Further, the overall secondary structure content of inclusion bodies is not significantly affected by subcellular compartmentalization, but may be altered at increased temperatures.

  18. A calorimetric determination of the enthalpy of formation and a description of the defect structure of the ordered beta-phase /Ni, Cu/ /1-x/ Al/x/

    NASA Technical Reports Server (NTRS)

    Henig, E. T.; Lukas, H. L.

    1988-01-01

    In order to describe thermodynamically the defect structure of an ordered B-Hume-Rothery phase, the heat of formation of (Ni,Cu)(1-x)Al(x) was measured at 1100 K as a function of concentration in the range x (sub Al) = 0.4 and 0.55 for three substitution rations x (sub Ni)/x (sub Cu) = infinity; 11; 5. The heat of formation of the NiAl beta-phase is strongly negative. For the stoichiometric composition it is -72.2 kJ/g-atom. On both the nickel-rich side and the aluminum-rich side the magnitude of the enthalpy of formation decreases linearly with concentration. Substitution of nickel for copper decreases the magnitude of the enthalpy of formation over the entire homogeneity range for the phase (Ni,Cu)(1-x)Al(x). The curve for the enthalpy of formation as well as the literature values for the chemical potential of aluminum are described with great accuracy by the disorder model of Wagner-Schottky.

  19. [1-butanol synthesis by Escherichia coli cells through butyryl-CoA formation by heterologous enzymes of clostridia and native enzymes of fatty acid beta-oxidation].

    PubMed

    Gulevich, A Iu; Skorokhodova, A Iu; Morzhakova, A A; Antonova, S V; Sukhozhenko, A V; Shakulov, R S; Debabov, V G

    2012-01-01

    Anaerobic biosynthesis of 1-butanol from glucose is investigated in recombinant Escherichia coli strains which form butyryl-CoA using the heterologous enzyme complex of clostridia or as a result of a reversal in the action of native enzymes of the fatty acid beta-oxidation pathway. It was revealed that when the basic pathways of acetic and lactic acid formation are inactivated due to deletions in the ackA, pta, poxB, and ldhA genes, the efficiency of butyryl-CoA biosynthesis and its reduced product, i.e., 1-butanol, by two types of recombinant stains is comparable. The limiting factor for 1-butanol production by the obtained strains is the low substrate specificity of the basic CoA-dependent alcohol/aldehyde AdhE dehydrogenase from E. coli to butyryl-CoA. It was concluded that, in order to construct an efficient 1-butanol producer based on a model strain synthesizing butyryl-CoA as a result of a reversal in fatty acid beta-oxidation enzymes, it is necessary to provide intensive formation of acetyl-CoA and enhanced activity of alternative alcohol and aldehyde dehydrogenases in the cells of a strain.

  20. Beta-D-glucosyl and alpha-D-galactosyl Yariv reagents: syntheses from p-nitrophenyl-D-glycosides by transfer reduction using ammonium formate.

    PubMed

    Basile, Dominick V; Ganjian, Iraj

    2004-12-15

    Yariv beta-D-glucosyl (4a) and Yariv alpha-d-galactosyl (4b) reagents are multivalent phenylglycosides. The beta-D-glucosyl reagent is considered diagnostic for arabinogalactan proteins (AGPs) to which it can reversibly bind, stain, and precipitate. The alpha-D-galactosyl reagent does not bind AGPs and is used as a control. In a new strategy, we accomplished the large scale synthesis of the Yariv reagents in one continuous step by a transfer reduction method and without a need for any specialized apparatus. As the starting material, p-nitrophenyl-D-glycosides (1) were reduced to p-aminophenyl-D-glycosides (2) using ammonium formate as the hydrogen donor. The excess formate was converted to formic acid and ammonia, which then were removed from the reaction by simple distillation. Without isolation, p-aminophenyl-D-glycosides were diazotized (3) and coupled to phloroglucinol to give the Yariv reagents in approximately 40% yield. AGPs are a major component of gum arabic, an emulsifying agent widely used in the food and pharmaceutical industries. Increasing interest in AGPs prompted the development of a relatively easy and inexpensive method for the synthesis of these reagents.

  1. Molten globule precursor states are conformationally correlated to amyloid fibrils of human beta-2-microglobulin.

    PubMed

    Skora, Lukasz; Becker, Stefan; Zweckstetter, Markus

    2010-07-14

    Misfolding intermediates play a key role in defining aberrant protein aggregation and amyloid formation in more than 15 different human diseases. However, their experimental characterization is challenging due to the transient nature and conformational heterogeneity of the involved states. Here, we demonstrate that direct carbon-detected NMR experiments allow observation, assignment, and structural analysis of molten globule amyloid intermediates that are severely broadened by conformational exchange. The method is used to characterize the structure and dynamics of partially unfolded intermediates of the 99-residue protein beta-2-microglobulin, which is the major component of insoluble aggregates occurring in dialysis-related amyloidosis. Comparison of the conformational properties of the molten globule-like intermediates with levels of deuterium incorporation into amyloid fibrils of beta-2-microglobulin revealed a close relationship between the conformational properties of the metastable intermediates and the beta-sheet-rich insoluble aggregates of beta-2-microglobulin.

  2. Beta amyloid and hyperphosphorylated tau deposits in the pancreas in type 2 diabetes

    SciTech Connect

    Miklossy, J.; Miller, L.; Qing, H.; Radenovic, A.; Kis, A.; Vileno, B.; Laszlo, F.; Martins, R.N.; Waeber, G.; Mooser, V.; Bosman, F.; Khalili, K.; Darbinian, N.; McGeer, P.L.

    2008-08-25

    Strong epidemiologic evidence suggests an association between Alzheimer disease (AD) and type 2 diabetes. To determine if amyloid beta (A{beta}) and hyperphosphorylated tau occurs in type 2 diabetes, pancreas tissues from 21 autopsy cases (10 type 2 diabetes and 11 controls) were analyzed. APP and tau mRNAs were identified in human pancreas and in cultured insulinoma beta cells (INS-1) by RT-PCR. Prominent APP and tau bands were detected by Western blotting in pancreatic extracts. Aggregated A{beta}, hyperphosphorylated tau, ubiquitin, apolipoprotein E, apolipoprotein(a), IB1/JIP-1 and JNK1 were detected in Langerhans islets in type 2 diabetic patients. A{beta} was co-localized with amylin in islet amyloid deposits. In situ beta sheet formation of islet amyloid deposits was shown by infrared microspectroscopy (SIRMS). LPS increased APP in non-neuronal cells as well. We conclude that A{beta} deposits and hyperphosphorylated tau are also associated with type 2 diabetes, highlighting common pathogenetic features in neurodegenerative disorders, including AD and type 2 diabetes and suggesting that A{beta} deposits and hyperphosphorylated tau may also occur in other organs than the brain.

  3. Early Mars climate near the Noachian-Hesperian boundary: Independent evidence for cold conditions from basal melting of the south polar ice sheet (Dorsa Argentea Formation) and implications for valley network formation

    NASA Astrophysics Data System (ADS)

    Fastook, James L.; Head, James W.; Marchant, David R.; Forget, Francois; Madeleine, Jean-Baptiste

    2012-05-01

    Currently, and throughout much of the Amazonian, the mean annual surface temperatures of Mars are so cold that basal melting does not occur in ice sheets and glaciers and they are cold-based. The documented evidence for extensive and well-developed eskers (sediment-filled former sub-glacial meltwater channels) in the south circumpolar Dorsa Argentea Formation is an indication that basal melting and wet-based glaciation occurred at the South Pole near the Noachian-Hesperian boundary. We employ glacial accumulation and ice-flow models to distinguish between basal melting from bottom-up heat sources (elevated geothermal fluxes) and top-down induced basal melting (elevated atmospheric temperatures warming the ice). We show that under mean annual south polar atmospheric temperatures (-100 °C) simulated in typical Amazonian climate experiments and typical Noachian-Hesperian geothermal heat fluxes (45-65 mW/m2), south polar ice accumulations remain cold-based. In order to produce significant basal melting with these typical geothermal heat fluxes, the mean annual south polar atmospheric temperatures must be raised from today's temperature at the surface (-100 °C) to the range of -50 to -75 °C. This mean annual polar surface atmospheric temperature range implies lower latitude mean annual temperatures that are likely to be below the melting point of water, and thus does not favor a "warm and wet" early Mars. Seasonal temperatures at lower latitudes, however, could range above the melting point of water, perhaps explaining the concurrent development of valley networks and open basin lakes in these areas. This treatment provides an independent estimate of the polar (and non-polar) surface temperatures near the Noachian-Hesperian boundary of Mars history and implies a cold and relatively dry Mars climate, similar to the Antarctic Dry Valleys, where seasonal melting forms transient streams and permanent ice-covered lakes in an otherwise hyperarid, hypothermal climate.

  4. Prostate formation in a marsupial is mediated by the testicular androgen 5 alpha-androstane-3 alpha,17 beta-diol.

    PubMed

    Shaw, G; Renfree, M B; Leihy, M W; Shackleton, C H; Roitman, E; Wilson, J D

    2000-10-24

    Development of the male urogenital tract in mammals is mediated by testicular androgens. It has been tacitly assumed that testosterone acts through its intracellular metabolite dihydrotestosterone (DHT) to mediate this process, but levels of these androgens are not sexually dimorphic in plasma at the time of prostate development. Here we show that the 3 alpha-reduced derivative of DHT, 5 alpha-androstane-3 alpha,17 beta-diol (5 alpha-adiol), is formed in testes of tammar wallaby pouch young and is higher in male than in female plasma in this species during early sexual differentiation. Administration of 5 alpha-adiol caused formation of prostatic buds in female wallaby pouch young, and in tissue minces of urogenital sinus and urogenital tubercle radioactive 5 alpha-adiol was converted to DHT, suggesting that circulating 5 alpha-adiol acts through DHT in target tissues. We conclude that circulating 5 alpha-adiol is a key hormone in male development.

  5. Adsorption and enzyme (beta-galactosidase and alpha-chymotrypsin): immobilization properties of gel fiber prepared by the gel formation of cellulose acetate and titanium iso-propoxide

    PubMed

    Kurokawa; Suzuki; Tamai

    1998-09-05

    We prepared a new composite gel fiber by the gel formation of cellulose acetate and titanium iso-propoxide. The fiber is harder than alginate gel; it is also stable in common solvents, phosphate solution, and electrolyte solutions over a wide range of pH from 3 to 10. The fiber shows amphoretic adsorption properties depending on pH, namely, it acts anionic with decreasing pH and cationic with increasing pH. However, the fiber had no adsorption property for a pyrogen endotoxin. The beta-galactosidase and alpha-chymotrypsin not retained in alginate gel were immobilized on the fibers by this method. The pH, temperature, and repeated run stabilities of the immobilized enzyme were compared to those of the native one. Copyright 1998 John Wiley & Sons, Inc.

  6. Transforming growth factor beta signaling is essential for the autonomous formation of cartilage-like tissue by expanded chondrocytes.

    PubMed

    Tekari, Adel; Luginbuehl, Reto; Hofstetter, Willy; Egli, Rainer J

    2015-01-01

    Cartilage is a tissue with limited self-healing potential. Hence, cartilage defects require surgical attention to prevent or postpone the development of osteoarthritis. For cell-based cartilage repair strategies, in particular autologous chondrocyte implantation, articular chondrocytes are isolated from cartilage and expanded in vitro to increase the number of cells required for therapy. During expansion, the cells lose the competence to autonomously form a cartilage-like tissue, that is in the absence of exogenously added chondrogenic growth factors, such as TGF-βs. We hypothesized that signaling elicited by autocrine and/or paracrine TGF-β is essential for the formation of cartilage-like tissue and that alterations within the TGF-β signaling pathway during expansion interfere with this process. Primary bovine articular chondrocytes were harvested and expanded in monolayer culture up to passage six and the formation of cartilage tissue was investigated in high density pellet cultures grown for three weeks. Chondrocytes expanded for up to three passages maintained the potential for autonomous cartilage-like tissue formation. After three passages, however, exogenous TGF-β1 was required to induce the formation of cartilage-like tissue. When TGF-β signaling was blocked by inhibiting the TGF-β receptor 1 kinase, the autonomous formation of cartilage-like tissue was abrogated. At the initiation of pellet culture, chondrocytes from passage three and later showed levels of transcripts coding for TGF-β receptors 1 and 2 and TGF-β2 to be three-, five- and five-fold decreased, respectively, as compared to primary chondrocytes. In conclusion, the autonomous formation of cartilage-like tissue by expanded chondrocytes is dependent on signaling induced by autocrine and/or paracrine TGF-β. We propose that a decrease in the expression of the chondrogenic growth factor TGF-β2 and of the TGF-β receptors in expanded chondrocytes accounts for a decrease in the activity of

  7. Architectural variability of confined turbidite sheet-sands: facies, geometry and infill of associated elementary channels. Examples from the Trois Evêchés Basin, Annot Sandstone Formation, SE France

    NASA Astrophysics Data System (ADS)

    Etienne, S.; Mulder, T.; Pace, A.; Bez, M.; Desaubliaux, G.

    2012-04-01

    The worldwide known Annot Sandstone Formation has been considered as a reference of confined siliciclastic turbidite system. This formation crops out in SE France and represents the Upper Eocene to Lower Oligocene gravitary infill of complex foreland basins, developed in front of the Alpine thrusts. This system can be assimilated as a sand-rich turbidite ramp, sourced by multiple fan deltas leading to topographically complex sub-basins. Highly bypassing channelized systems dominate in the most proximal and most confined areas. They distally evolve to relatively less confined areas, in which sedimentary bodies appear to be more continuous and homogenous on a regional scale. These last architectural elements, defined as sheet-sands or depositional lobes, have been the focus of this study in poorly documented areas. From an important dataset made of very high resolution outcrop correlations (gathered mainly in the Trois Evêchés and Lauzanier sub-basins), we have quantified the complex distribution of sedimentary facies and structures, grain-size and key surfaces in sand-rich sheets. This was done to understand their variability from depositional event to architectural element scales and to better characterize dimensions and characteristics of their components. Six main types of architectural elements were defined, composed of both channelized and unchannelized elements. Channelized units show a high variability in terms of facies, geometry and patterns of infill that are related to multiple erosional and depositional processes, which will be discussed. We notably relate some evidences of sinuous channels, represented by lateral accretion deposits in the channel complex axis and by low angle cross-bedded facies. We interpret this particular facies as the result of flow deconfinement and overbanks above channel margins. The stratigraphic analysis of elementary objects allows us to propose a genetic model and a spatial distribution model of sheet-sand architectural

  8. Glacial landforms on German Bank, Scotian Shelf: evidence for Late Wisconsinan ice-sheet dynamics and implications for the formation of De Geer moraines

    USGS Publications Warehouse

    Todd, Brian J.; Valentine, Page C.; Longva, Oddvar; Shaw, John

    2007-01-01

    The extent and behaviour of the southeast margin of the Laurentide Ice Sheet in Atlantic Canada is of significance in the study of Late Wisconsinan ice sheet-ocean interactions. Multibeam sonar imagery of subglacial, ice-marginal and glaciomarine landforms on German Bank, Scotian Shelf, provides evidence of the pattern of glacial-dynamic events in the eastern Gulf of Maine. Northwest-southeast trending drumlins and megaflutes dominate northern German Bank. On southern German Bank, megaflutes of thin glacial deposits create a distinct northwest-southeast grain. Lobate regional moraines (>10km long) are concave to the northwest, up-ice direction and strike southwest-northeast, normal to the direction of ice flow. Ubiquitous, overlying De Geer moraines (

  9. Soluble amyloid beta oligomers block the learning-induced increase in hippocampal sharp wave-ripple rate and impair spatial memory formation.

    PubMed

    Nicole, Olivier; Hadzibegovic, Senka; Gajda, Judyta; Bontempi, Bruno; Bem, Tiaza; Meyrand, Pierre

    2016-03-07

    Post-learning hippocampal sharp wave-ripples (SWRs) generated during slow wave sleep are thought to play a crucial role in memory formation. While in Alzheimer's disease, abnormal hippocampal oscillations have been reported, the functional contribution of SWRs to the typically observed spatial memory impairments remains unclear. These impairments have been related to degenerative synaptic changes produced by soluble amyloid beta oligomers (Aβos) which, surprisingly, seem to spare the SWR dynamics during routine behavior. To unravel a potential effect of Aβos on SWRs in cognitively-challenged animals, we submitted vehicle- and Aβo-injected mice to spatial recognition memory testing. While capable of forming short-term recognition memory, Aβ mice exhibited faster forgetting, suggesting successful encoding but an inability to adequately stabilize and/or retrieve previously acquired information. Without prior cognitive requirements, similar properties of SWRs were observed in both groups. In contrast, when cognitively challenged, the post-encoding and -recognition peaks in SWR occurrence observed in controls were abolished in Aβ mice, indicating impaired hippocampal processing of spatial information. These results point to a crucial involvement of SWRs in spatial memory formation and identify the Aβ-induced impairment in SWRs dynamics as a disruptive mechanism responsible for the spatial memory deficits associated with Alzheimer's disease.

  10. Analysis of small latent transforming growth factor-beta complex formation and dissociation by surface plasmon resonance. Absence of direct interaction with thrombospondins.

    PubMed

    Bailly, S; Brand, C; Chambaz, E M; Feige, J J

    1997-06-27

    Transforming growth factor-beta (TGFbeta) is a pluripotent regulator of cell growth and differentiation. The growth factor is expressed as a latent complex that must be converted to an active form before interacting with its ubiquitous high affinity receptors. This conversion involves the release of the mature TGFbeta through disruption of the noncovalent interactions with its propeptide or latency associated protein (LAP). Complex formation or dissociation between LAP and TGFbeta plays a very important role in TGFbeta biological activity at different steps. To further characterize the kinetic parameters of this interaction, we have employed surface plasmon resonance biosensor methodology. Using this technique, we observed real time association of LAP with mature TGFbeta1. The complex formation showed an equilibrium Kd around 3-7 nM. Furthermore, we observed dissociation of the complex in the presence of extreme pH, chaotropic agents, or plasmin, confirming their effects on TGFbeta activation. The same approach was used to examine whether latent TGFbeta1 could interact with thrombospondins, previously described as activators of latent TGFbeta. Using this method, we could not detect any direct interaction of thrombospondins with either LAP alone, TGFbeta1 alone, or the small latent TGFbeta1 complex. This suggests that activation of latent TGFbeta1 complex by thrombospondins is through an indirect mechanism.

  11. Soluble amyloid beta oligomers block the learning-induced increase in hippocampal sharp wave-ripple rate and impair spatial memory formation

    PubMed Central

    Nicole, Olivier; Hadzibegovic, Senka; Gajda, Judyta; Bontempi, Bruno; Bem, Tiaza; Meyrand, Pierre

    2016-01-01

    Post-learning hippocampal sharp wave-ripples (SWRs) generated during slow wave sleep are thought to play a crucial role in memory formation. While in Alzheimer’s disease, abnormal hippocampal oscillations have been reported, the functional contribution of SWRs to the typically observed spatial memory impairments remains unclear. These impairments have been related to degenerative synaptic changes produced by soluble amyloid beta oligomers (Aβos) which, surprisingly, seem to spare the SWR dynamics during routine behavior. To unravel a potential effect of Aβos on SWRs in cognitively-challenged animals, we submitted vehicle- and Aβo-injected mice to spatial recognition memory testing. While capable of forming short-term recognition memory, Aβ mice exhibited faster forgetting, suggesting successful encoding but an inability to adequately stabilize and/or retrieve previously acquired information. Without prior cognitive requirements, similar properties of SWRs were observed in both groups. In contrast, when cognitively challenged, the post-encoding and -recognition peaks in SWR occurrence observed in controls were abolished in Aβ mice, indicating impaired hippocampal processing of spatial information. These results point to a crucial involvement of SWRs in spatial memory formation and identify the Aβ-induced impairment in SWRs dynamics as a disruptive mechanism responsible for the spatial memory deficits associated with Alzheimer’s disease. PMID:26947247

  12. Sugar fragmentation in the maillard reaction cascade: isotope labeling studies on the formation of acetic acid by a hydrolytic beta-dicarbonyl cleavage mechanism.

    PubMed

    Davídek, Tomas; Devaud, Stéphanie; Robert, Fabien; Blank, Imre

    2006-09-06

    The formation of acetic acid was elucidated based on volatile reaction products and related nonvolatile key intermediates. The origin and yield of acetic acid were determined under well-controlled conditions (90-120 degrees C, pH 6-8). Experiments with various 13C-labeled glucose isotopomers in the presence of glycine revealed all six carbon atoms being incorporated into acetic acid: C-1/C-2 ( approximately 70%), C-3/C-4 ( approximately 10%), and C-5/C-6 (approximately 20%). Acetic acid is a good marker of the 2,3-enolization pathway since it is almost exclusively formed from 1-deoxy-2,3-diulose intermediates. Depending on the pH, the acetic acid conversion yield reached 85 mol % when using 1-deoxy-2,3-hexodiulose (1) as a precursor. Hydrolytic beta-dicarbonyl cleavage of 1-deoxy-2,4-hexodiuloses was shown to be the major pathway leading to acetic acid from glucose without the intermediacy of any oxidizing agents. The presence of key intermediates was corroborated for the first time, i.e., tetroses and 2-hydroxy-3-oxobutanal, a tautomer of 1-hydroxy-2,3-butanedione, also referred to as 1-deoxy-2,3-tetrodiulose. The hydrolytic beta-dicarbonyl cleavage represents a general pathway to organic acids, which corresponds to an acyloin cleavage or a retro-Claisen type reaction. Although alternative mechanisms must exist, the frequently reported hydrolytic alpha-dicarbonyl cleavage of 1 can be ruled out as a pathway forming carboxylic acids.

  13. Molecular basis for amyloid-[beta] polymorphism

    SciTech Connect

    Colletier, Jacques-Philippe; Laganowsky, Arthur; Landau, Meytal; Zhao, Minglei; Soriaga, Angela B.; Goldschmidt, Lukasz; Flot, David; Cascio, Duilio; Sawaya, Michael R.; Eisenberga, David

    2011-10-19

    Amyloid-beta (A{beta}) aggregates are the main constituent of senile plaques, the histological hallmark of Alzheimer's disease. A{beta} molecules form {beta}-sheet containing structures that assemble into a variety of polymorphic oligomers, protofibers, and fibers that exhibit a range of lifetimes and cellular toxicities. This polymorphic nature of A{beta} has frustrated its biophysical characterization, its structural determination, and our understanding of its pathological mechanism. To elucidate A{beta} polymorphism in atomic detail, we determined eight new microcrystal structures of fiber-forming segments of A{beta}. These structures, all of short, self-complementing pairs of {beta}-sheets termed steric zippers, reveal a variety of modes of self-association of A{beta}. Combining these atomic structures with previous NMR studies allows us to propose several fiber models, offering molecular models for some of the repertoire of polydisperse structures accessible to A{beta}. These structures and molecular models contribute fundamental information for understanding A{beta} polymorphic nature and pathogenesis.

  14. Helix formation in preorganized beta/gamma-peptide foldamers: hydrogen-bond analogy to the alpha-helix without alpha-amino acid residues.

    PubMed

    Guo, Li; Almeida, Aaron M; Zhang, Weicheng; Reidenbach, Andrew G; Choi, Soo Hyuk; Guzei, Ilia A; Gellman, Samuel H

    2010-06-16

    We report the first high-resolution structural data for the beta/gamma-peptide 13-helix (i,i+3 C=O...H-N H-bonds), a secondary structure that is formed by oligomers with a 1:1 alternation of beta- and gamma-amino acid residues. Our characterization includes both crystallographic and 2D NMR data. Previous studies suggested that beta/gamma-peptides constructed from conformationally flexible residues adopt a different helical secondary structure in solution. Our design features preorganized beta- and gamma-residues, which strongly promote 13-helical folding by the 1:1 beta/gamma backbone.

  15. Solid-state NMR analysis of the {beta}-strand orientation of the protofibrils of amyloid {beta}-protein

    SciTech Connect

    Doi, Takashi; Masuda, Yuichi; Irie, Kazuhiro; Akagi, Ken-ichi; Monobe, Youko; Imazawa, Takayoshi; Takegoshi, K.

    2012-11-30

    Highlights: Black-Right-Pointing-Pointer The supramolecular structure of A{beta}42 protofibrils was analyzed by solid-state NMR. Black-Right-Pointing-Pointer The Ala-21 residue in the A{beta}42 protofibrils is included in a slightly disordered {beta}-strand. Black-Right-Pointing-Pointer The A{beta}42 protofibrils do not form intermolecular in-register parallel {beta}-sheets. -- Abstract: Alzheimer's disease (AD) is caused by abnormal deposition (fibrillation) of a 42-residue amyloid {beta}-protein (A{beta}42) in the brain. During the process of fibrillation, the A{beta}42 takes the form of protofibrils with strong neurotoxicity, and is thus believed to play a crucial role in the pathogenesis of AD. To elucidate the supramolecular structure of the A{beta}42 protofibrils, the intermolecular proximity of the Ala-21 residues in the A{beta}42 protofibrils was analyzed by {sup 13}C-{sup 13}C rotational resonance experiments in the solid state. Unlike the A{beta}42 fibrils, an intermolecular {sup 13}C-{sup 13}C correlation was not found in the A{beta}42 protofibrils. This result suggests that the {beta}-strands of the A{beta}42 protofibrils are not in an in-register parallel orientation. A{beta}42 monomers would assemble to form protofibrils with the {beta}-strand conformation, then transform into fibrils by forming intermolecular parallel {beta}-sheets.

  16. Beta Blockers

    MedlinePlus

    Diseases and Conditions High blood pressure (hypertension) Beta blockers, also called beta-adrenergic blocking agents, treat a variety of conditions, such as high blood pressure and migraines. Find out more about this ...

  17. MESSENGER and Venus Express Observations of the Near-tail of Venus: Magnetic Flux Transport, Current Sheet Structure, and Flux Rope Formation

    NASA Technical Reports Server (NTRS)

    Slavin, James A.; Boardsen, S. A.; Sarantos, M.; Acuna, M. H.; Anderson, B. J.; Barabash, S.; Benna, M.; Fraenz, M.; Gloeckler, G.; Gold, R. E.; Ho, G. C.; Korth, H.; Krimigis, S. M.; McNutt, R. L., Jr.; Raines, J. M.; Solomon, S. C.; Zhang, T.-L.; Zurbuchen, T. H.

    2008-01-01

    At 23:08 UT on 5 June 2007 the MESSENGER spacecraft reached its closest approach altitude (338 km) during its second flyby of Venus en route to its 2011 orbit insertion at Mercury. Whereas no measurements were collected during MESSENGER'S first Venus flyby in October 2006, the Magnetometer (MAG) and the Energetic Particle and Plasma Spectrometer (EPPS) operated successfully throughout this second encounter. Venus provides the solar system's best example to date of a solar wind - ionosphere planetary interaction. We present MESSENGER observations of the near-tail of Venus with emphasis on determining the time scales for magnetic flux transport, the structure of the cross-tail current sheet at very low altitudes (approx. 300 to 1000 km), and the nature and origin of a magnetic flux rope observed in the current sheet. The availability of the simultaneous Venus Express upstream measurements provides a unique opportunity to examine the influence of solar wind plasma and interplanetary magnetic field conditions on this planet's solar wind interaction at solar minimum.

  18. Near-earth Thin Current Sheets and Birkeland Currents during Substorm Growth Phase

    SciTech Connect

    Sorin Zaharia; C.Z. Cheng

    2003-04-30

    Two important phenomena observed during the magnetospheric substorm growth phase are modeled: the formation of a near-Earth (|X| {approx} 9 R{sub E}) thin cross-tail current sheet, as well as the equatorward shift of the ionospheric Birkeland currents. Our study is performed by solving the 3-D force-balance equation with realistic boundary conditions and pressure distributions. The results show a cross-tail current sheet with large current (J{sub {phi}} {approx} 10 nA/m{sup 2}) and very high plasma {beta} ({beta} {approx} 40) between 7 and 10 R{sub E}. The obtained region-1 and region-2 Birkeland currents, formed on closed field lines due to pressure gradients, move equatorward and become more intense (J{sub {parallel}max} {approx} 3 {micro}A/m{sup 2}) compared to quiet times. Both results are in agreement with substorm growth phase observations. Our results also predict that the cross-tail current sheet maps into the ionosphere in the transition region between the region-1 and region-2 currents.

  19. Study of formation of deep trapping mechanism by UV, beta and gamma irradiated Eu(3+) activated SrY2O4 and Y4Al2O9 phosphors.

    PubMed

    Dubey, Vikas; Kaur, Jagjeet; Parganiha, Yogita; Suryanarayana, N S; Murthy, K V R

    2016-04-01

    This paper reports the thermoluminescence properties of Eu(3+) doped different host matrix phosphors (SrY2O4 and Y4Al2O9). The phosphor is prepared by high temperature solid state reaction method. The method is suitable for large scale production and fixed concentration of boric acid using as a flux. The prepared samples were characterized by X-ray diffraction technique and the crystallite size calculated by Scherer's formula. The prepared phosphor characterized by Scanning Electron Microscopic (SEM), Fourier Transform Infrared (FTIR), Energy Dispersive X-ray analysis (EDX), thermoluminescence (TL) and Transmission Electron Microscopic (TEM) techniques. The prepared phosphors for different concentration of Eu(3+) ions were examined by TL glow curve for UV, beta and gamma irradiation. The UV 254nm source used for UV irradiation, Sr(90) source was used for beta irradiation and Co(60) source used for gamma irradiation. SrY2O4:Eu(3+)and Y4Al2O9:Eu(3+) phosphors which shows both higher temperature peaks and lower temperature peaks for UV, beta and gamma irradiation. Here UV irradiated sample shows the formation of shallow trap (surface trapping) and the gamma irradiated sample shows the formation of deep trapping. The estimation of trap formation was evaluated by knowledge of trapping parameters. The trapping parameters such as activation energy, order of kinetics and frequency factor were calculated by peak shape method. Here most of the peak shows second order of kinetics. The effect of gamma, beta and UV exposure on TL studies was also examined and it shows linear response with dose which indicate that the samples may be useful for TL dosimetry. Formation of deep trapping mechanism by UV, beta and gamma irradiated Eu(3+) activated SrY2O4 and Y4Al2O9 phosphors is discussed in this paper.

  20. Proteopedia: Rossmann Fold: A Beta-Alpha-Beta Fold at Dinucleotide Binding Sites

    ERIC Educational Resources Information Center

    Hanukoglu, Israel

    2015-01-01

    The Rossmann fold is one of the most common and widely distributed super-secondary structures. It is composed of a series of alternating beta strand (ß) and alpha helical (a) segments wherein the ß-strands are hydrogen bonded forming a ß-sheet. The initial beta-alpha-beta (ßaß) fold is the most conserved segment of Rossmann folds. As this segment…

  1. Discovery of DNA dyes Hoechst 34580 and 33342 as good candidates for inhibiting amyloid beta formation: in silico and in vitro study

    NASA Astrophysics Data System (ADS)

    Thai, Nguyen Quoc; Tseng, Ning-Hsuan; Vu, Mui Thi; Nguyen, Tin Trung; Linh, Huynh Quang; Hu, Chin-Kun; Chen, Yun-Ru; Li, Mai Suan

    2016-08-01

    Combining Lipinski's rule with the docking and steered molecular dynamics simulations and using the PubChem data base of about 1.4 million compounds, we have obtained DNA dyes Hoechst 34580 and Hoechst 33342 as top-leads for the Alzheimer's disease. The binding properties of these ligands to amyloid beta (Aβ) fibril were thoroughly studied by in silico and in vitro experiments. Hoechst 34580 and Hoechst 33342 prefer to locate near hydrophobic regions with binding affinity mainly governed by the van der Waals interaction. By the Thioflavin T assay, it was found that the inhibition constant IC50 ≈ 0.86 and 0.68 μM for Hoechst 34580 and Hoechst 33342, respectively. This result qualitatively agrees with the binding free energy estimated using the molecular mechanic-Poisson Boltzmann surface area method and all-atom simulations with the AMBER-f99SB-ILDN force field and water model TIP3P. In addition, DNA dyes have the high capability to cross the blood brain barrier. Thus, both in silico and in vitro experiments have shown that Hoechst 34580 and 33342 are good candidates for treating the Alzheimer's disease by inhibiting Aβ formation.

  2. The magnetohydrodynamics of current sheets

    NASA Technical Reports Server (NTRS)

    Priest, E. R.

    1985-01-01

    Examples of current sheets are summarized and their formation is described. A universal phenomenon in cosmic plasmas is the creation of sheets off intense current near X-type neutral points (where the magnetic field vanishes). These sheets are important as sites where the magnetic-field energy is converted efficiently into heat and bulk kinetic energy and where particles can be accelerated to high energies. Examples include disruptions in laboratory tokamaks, substorms in the earth's magnetosphere, and flares on the sun. The basic behavior of a one-dimensional sheet is presented, together with an account of the linear tearing-mode instability that can cause the field lines in such a sheet to reconnect. Such reconnection may develop in different ways: it may arise from a spontaneous instability or it may be driven, either from outside by motions or locally by a resistivity enhancement. Various processes are described that may occur during the nonlinear development of tearing, along with the many numerical and laboratory experiments that are aiding our understanding of this intriguing cosmical process.

  3. Enhanced silver ion binding to a rigid bisarene molecular cleft with formation of nonpolar pleated sheets through non-ionic intermolecular forces.

    PubMed

    Gogoll, Adolf; Polavarapu, Prasad; Grennberg, Helena

    2007-06-25

    Silver ion complexation to bisarene ligands is enhanced by providing a conformationally rigid molecular cleft in the (Z)-acenaphthylene dimer 1. NMR titrations were used to determine complexation constants K for a series of ligands in tetrahydrofuran solution, with K = 4.9 M(-1) for the Z dimer 1 and 0.4 M(-1) for the E dimer 2. Higher values of K were observed in CDCl(3)/CD(3)OD 9:1 with K = 38 M(-1) for 1 and K = 4.1 M(-1) for 2. In the solid state, isolated clusters of [1 x (AgCF(3)SO(3))(2)](2) form a novel, pleated-sheet motif based on non-ionic interactions between clusters.

  4. Graphitization behaviour of chemically derived graphene sheets.

    PubMed

    Long, Donghui; Li, Wei; Qiao, Wenming; Miyawaki, Jin; Yoon, Seong-Ho; Mochida, Isao; Ling, Licheng

    2011-09-01

    Graphene sheets were prepared via chemical reduction of graphite oxides and then graphitized at 2800 °C. The structure changes from pristine graphite to graphitized graphene sheets were monitored using X-ray diffraction and Raman spectroscopy. It was found that the graphitized graphene sheets exhibited relatively low degree of graphitization and high level of structural defects. XPS spectra revealed that oxygen functionalities could be completely eliminated after graphitization. Morphology observations indicated that graphitization could induce the coalescence and connection of the crumpled graphene agglomerations into compressed grains. The connections included the joint of graphitic sheets along the c-axis with van der Waals force between graphitic sheets and the joint of sheets in the in-plane with covalent bond between carbon atoms. New structures such as the formation of loop at the tip of graphene sheets and the formation of 3D concentric graphene nanoparticles occurred in the graphitized graphene sheets, as a result of self-organization to achieve their lowest potential energy. Our findings should provide some experimental implications for understanding of graphitization behaviour and thermal stability of strictly 2D graphene monolayers.

  5. Beta experiment

    NASA Technical Reports Server (NTRS)

    1982-01-01

    A focused laser doppler velocimeter (LDV) system was developed for the measurement of atmospheric backscatter (beta) from aerosols at infrared wavelengths. A Doppler signal generator was used in mapping the coherent sensitive focal volume of a focused LDV system. System calibration data was analyzed during the flight test activity scheduled for the Beta system. These analyses were performed to determine the acceptability of the Beta measurement system's performance.

  6. Experimental Study of Lower-hybrid Drift Turbulence in a Reconnecting Current Sheet

    SciTech Connect

    Carter, T. A.; Yamada, M.; Ji, H.; Kulsrud, R. M.; Trintchouck, F.

    2002-06-18

    The role of turbulence in the process of magnetic reconnection has been the subject of a great deal of study and debate in the theoretical literature. At issue in this debate is whether turbulence is essential for fast magnetic reconnection to occur in collisionless current sheets. Some theories claim it is necessary in order to provide anomalous resistivity, while others present a laminar fast reconnection mechanism based on the Hall term in the generalized Ohm's law. In this work, a thorough study of electrostatic potential fluctuations in the current sheet of the Magnetic Reconnection Experiment (MRX) [M. Yamada et al., Phys. Plasmas 4, 1936 (1997)] was performed in order to ascertain the importance of turbulence in a laboratory reconnection experiment. Using amplified floating Langmuir probes, broadband fluctuations in the lower hybrid frequency range (fLH approximately 5-15 MHz) were measured which arise with the formation of the current sheet in MRX. The frequency spectrum, spatial amplitude profile, and spatial correlation characteristics of the measured turbulence were examined carefully, finding consistency with theories of the lower-hybrid drift instability (LHDI). The LHDI and its role in magnetic reconnection has been studied theoretically for decades, but this work represents the first detection and detailed study of the LHDI in a laboratory current sheet. The observation of the LHDI in MRX has provided the unique opportunity to uncover the role of this instability in collisionless reconnection. It was found that: (1) the LHDI fluctuations are confined to the low-beta edge of current sheets in MRX; (2) the LHDI amplitude does not correlate well in time or space with the reconnection electric field, which is directly related to the rate of reconnection; and (3) significant LHDI amplitude persists in high collisionality current sheets where the reconnection rate is classical. These findings suggest that the measured LHDI fluctuations do not play an

  7. Structural Biology Fact Sheet

    MedlinePlus

    ... Home > Science Education > Structural Biology Fact Sheet Structural Biology Fact Sheet Tagline (Optional) Middle/Main Content Area What is structural biology? Structural biology is a field of science focused ...

  8. Zika Virus Fact Sheet

    MedlinePlus

    ... sheets Fact files Questions & answers Features Multimedia Contacts Zika virus Fact sheet Updated 6 September 2016 Key ... and last for 2-7 days. Complications of Zika virus disease Based on a systematic review of ...

  9. Uterine Fibroids Fact Sheet

    MedlinePlus

    ... Topics Uterine fibroids fact sheet (PDF, 950 KB) FDA warning on power morcellators in treatment for uterine ... Topics Uterine fibroids fact sheet (PDF, 950 KB) FDA warning on power morcellators in treatment for uterine ...

  10. Zinc-induced heterodimer formation between metal-binding domains of intact and naturally modified amyloid-beta species: implication to amyloid seeding in Alzheimer's disease?

    PubMed

    Mezentsev, Yuri V; Medvedev, Alexei E; Kechko, Olga I; Makarov, Alexander A; Ivanov, Alexis S; Mantsyzov, Alexey B; Kozin, Sergey A

    2016-11-01

    Zinc ions and modified amyloid-beta peptides (Aβ) play a critical role in the pathological aggregation of endogenous Aβ in Alzheimer's disease (AD). Zinc-induced Aβ oligomerization is mediated by the metal-binding domain (MBD) which includes N-terminal residues 1-16 (Aβ1-16). Earlier, it has been shown that Aβ1-16 as well as some of its naturally occurring variants undergoes zinc-induced homodimerization via the interface in which zinc ion is coordinated by Glu11 and His14 of the interacting subunits. In this study using surface plasmon resonance technique, we have found that in the presence of zinc ions Aβ1-16 forms heterodimers with MBDs of two Aβ species linked to AD: Aβ containing isoAsp7 (isoAβ) and Aβ containing phosphorylated Ser8 (pS8-Aβ). The heterodimers appear to possess the same interface as the homodimers. Simulation of 200 ns molecular dynamic trajectories in two constructed models of dimers ([Aβ1-16/Zn/Aβ1-16] and [isoAβ1-16/Zn/Aβ1-16]), has shown that conformational flexibility of the N-terminal fragments of the dimer subunits is controlled by the structure of corresponding sites 6-8. The data suggest that isoAβ and pS8-Aβ can be involved in the AD pathogenesis by means of their zinc-dependent interactions with endogenous Aβ resulting in the formation of heterodimeric seeds for amyloid aggregation.

  11. The cytological changes of tobacco zygote and proembryo cells induced by beta-glucosyl Yariv reagent suggest the involvement of arabinogalactan proteins in cell division and cell plate formation

    PubMed Central

    2012-01-01

    Background In dicotyledonous plant, the first asymmetric zygotic division and subsequent several cell divisions are crucial for proembryo pattern formation and later embryo development. Arabinogalactan proteins (AGPs) are a family of extensively glycosylated cell surface proteins that are thought to have important roles in various aspects of plant growth and development, including embryogenesis. Previous results from our laboratory show that AGPs are concerned with tobacco egg cell fertilization and zygotic division. However, how AGPs interact with other factors involved in zygotic division and proembryo development remains unknown. Results In this study, we used the tobacco in vitro zygote culture system and series of meticulous cell biology techniques to investigate the roles of AGPs in zygote and proembryo cell division. For the first time, we examined tobacco proembryo division patterns detailed to every cell division. The bright-field images and statistical results both revealed that with the addition of an exogenous AGPs inhibitor, beta-glucosyl Yariv (beta-GlcY) reagent, the frequency of aberrant division increased remarkably in cultured tobacco zygotes and proembryos, and the cell plate specific locations of AGPs were greatly reduced after beta-GlcY treatment. In addition, the accumulations of new cell wall materials were also significantly affected by treating with beta-GlcY. Detection of cellulose components by Calcofluor white stain showed that strong fluorescence was located in the newly formed wall of daughter cells after the zygotic division of in vivo samples and the control samples from in vitro culture without beta-GlcY treatment; while there was only weak fluorescence in the newly formed cell walls with beta-GlcY treatment. Immunocytochemistry examination with JIM5 and JIM7 respectively against the low- and high-esterified pectins displayed that these two pectins located in opposite positions of zygotes and proembryos in vivo and the polarity was

  12. Evolution of wheat gliadins conformation during film formation: a fourier transform infrared study.

    PubMed

    Mangavel, C; Barbot, J; Popineau, Y; Guéguen, J

    2001-02-01

    The secondary structures of wheat gliadins (a major storage protein fraction from gluten) in film-forming solutions and their evolution during film formation were investigated by Fourier transform infrared spectroscopy. In the film-forming solution, wheat gliadins presented a mixture of different secondary structures, with an important contribution of beta-turns induced by proline residues. The presence of plasticizer did not have any influence on protein secondary structure in the film-forming solution. The evolution of protein conformation was followed during drying; the major feature of this evolution was a clear growing of the infrared band at 1622 cm(-1), characteristic of intermolecular hydrogen-bonded beta-sheets. This revealed the formation of protein aggregates during film drying. The influence of the drying temperature on film properties and gliadin secondary structures was also investigated. Higher drying temperatures induced an increase of both the tensile strength of the films and the amount of beta-sheets aggregates. Although the appearance of heat-induced disulfide bridge cross-links has already been described, there is clear evidence that hydrogen-bonded beta-sheets aggregates are also induced by thermal treatment. It was not possible, however, to determine whether there is a direct relationship between the occurrence of these aggregates and the increase of the tensile strength of the films.

  13. Isotopically sensitive branching in the formation of cyclic monoterpenes: proof that (-)-alpha-pinene and (-)-beta-pinene are synthesized by the same monoterpene cyclase via deprotonation of a common intermediate

    SciTech Connect

    Croteau, R.B.; Wheeler, C.J.; Cane, D.E.; Ebert, R.; Ha, H.J.

    1987-08-25

    To determine whether the bicyclic monoterpene olefins (-)-alpha-pinene and (-)-beta-pinene arise biosynthetically from the same monoterpene cyclase by alternate deprotonations of a common carbocationic intermediate, the product distributions arising from the acyclic precursor (10-/sup 2/H/sub 3/,1-/sup 3/H)geranyl pyrophosphate were compared with those resulting from incubation of (1-3H)geranyl pyrophosphate with (-)-pinene cyclase from Salvia officinalis. Alteration in proportions of the olefinic products generated by the partially purified pinene cyclase resulted from the suppression of the formation of (-)-beta-pinene (C10 deprotonation) by a primary deuterium isotope effect with a compensating stimulation of the formation of (-)-alpha-pinene (C4 deprotonation). (-)-Pinene cyclase as well as (+)-pinene cyclase also exhibited a decrease in the proportion of the acyclic olefin myrcene generated from the deuteriated substrate, accompanied by a corresponding increase in the commitment to cyclized products. The observation of isotopically sensitive branching, in conjunction with quantitation of the magnitude of the secondary deuterium isotope effect on the overall rate of product formation by the (+)- and (-)-pinene cyclases as well as two other monoterpene cyclases from the same tissue, supports the biosynthetic origin of (-)-alpha-pinene and (-)-beta-pinene by alternative deprotonations of a common enzymatic intermediate. A biogenetic scheme consistent with these results is presented, and alternate proposals for the origin of the pinenes are addressed.

  14. Heparin and Methionine Oxidation Promote the Formation of Apolipoprotein A-I Amyloid Comprising α-Helical and β-Sheet Structures.

    PubMed

    Townsend, David; Hughes, Eleri; Hussain, Rohanah; Siligardi, Giuliano; Baldock, Sarah; Madine, Jillian; Middleton, David A

    2017-03-13

    Peptides derived from apolipoprotein A-I (apoA-I), the main component of high-density lipoprotein (HDL), constitute the main component of amyloid deposits that colocalize with atherosclerotic plaques. Here we investigate the molecular details of full-length, lipid-deprived apoA-I after assembly into insoluble aggregates under physiologically relevant conditions known to induce aggregation in vitro. Unmodified apoA-I is shown to remain soluble at pH 7 for at least 3 days, retaining its native α-helical-rich structure. Upon acidification to pH 4, apoA-I rapidly assembles into insoluble nonfibrillar aggregates lacking the characteristic cross-β features of amyloid. In the presence of heparin, the rate and thioflavin T responsiveness of the aggregates formed at pH 4 increase and short amyloid-like fibrils are observed, which give rise to amyloid-characteristic X-ray reflections at 4.7 and 10 Å. Solid-state nuclear magnetic resonance (SSNMR) and synchrotron radiation circular dichroism spectroscopy of fibrils formed in the presence of heparin show they retain some α-helical characteristics together with new β-sheet structures. Interestingly, SSNMR indicates a similar molecular structure of aggregates formed in the absence of heparin at pH 6 after oxidation of the three methionine residues, although their morphology is rather different from that of the heparin-derived fibrils. We propose a model for apoA-I aggregation in which perturbations of a four-helix bundle-like structure, induced by interactions of heparin or methionine oxidation, cause the partially helical N-terminal residues to disengage from the remaining, intact helices, thereby allowing self-assembly via β-strand associations.

  15. Evolution of outer membrane beta-barrels from an ancestral beta beta hairpin.

    PubMed

    Remmert, M; Biegert, A; Linke, D; Lupas, A N; Söding, J

    2010-06-01

    Outer membrane beta-barrels (OMBBs) are the major class of outer membrane proteins from Gram-negative bacteria, mitochondria, and plastids. Their transmembrane domains consist of 8-24 beta-strands forming a closed, barrel-shaped beta-sheet around a central pore. Despite their obvious structural regularity, evidence for an origin by duplication or for a common ancestry has not been found. We use three complementary approaches to show that all OMBBs from Gram-negative bacteria evolved from a single, ancestral beta beta hairpin. First, we link almost all families of known single-chain bacterial OMBBs with each other through transitive profile searches. Second, we identify a clear repeat signature in the sequences of many OMBBs in which the repeating sequence unit coincides with the structural beta beta hairpin repeat. Third, we show that the observed sequence similarity between OMBB hairpins cannot be explained by structural or membrane constraints on their sequences. The third approach addresses a longstanding problem in protein evolution: how to distinguish between a very remotely homologous relationship and the opposing scenario of "sequence convergence." The origin of a diverse group of proteins from a single hairpin module supports the hypothesis that, around the time of transition from the RNA to the protein world, proteins arose by amplification and recombination of short peptide modules that had previously evolved as cofactors of RNAs.

  16. Differences in beta-adrenergic regulation of cyclic AMP formation in cerebral cortical slices of the rat and spiny mouse--Acomys cahirinus.

    PubMed

    Chalecka-Franaszek, E; Nalepa, I; Vetulani, J

    1990-01-01

    In both the rat and Acomys cahirinus the adrenergic cyclic AMP generating system in the brain is dependent not only on beta-, but also on alpha-adrenoceptors. The relative role of alpha-adrenoceptors is much greater in the Acomys cahirinus. This feature makes the Acomys an interesting animal model for investigating the role of alpha-beta-adrenoceptor coupling in generation of cyclic AMP and the mechanism of action of antidepressant treatment.

  17. Structural Studies of Copper(I) Complexes of Amyloid-Beta Peptide Fragments: Formation of Two-Coordinate Bis(Histidine) Complexes

    SciTech Connect

    Himes, R.A.; Park, G.Young.; Siluvai, G.Sutha.; Blackburn, N.J.; Karlin, K.D.

    2009-05-18

    The beta bind: Copper(I) binds to amyloid {beta}-peptide fragments (see structure) as a stable bis(histidine), two-coordinate, near-linear complex, even in the presence of potential additional ligands. As has been proposed or assumed in other studies, the copper(I)-peptide complexes react with dioxygen to form the reactive oxygen species H{sub 2}O{sub 2}, without the need for a third histidine ligand to promote the chemistry.

  18. MHD Ballooning Instability in the Plasma Sheet

    SciTech Connect

    C.Z. Cheng; S. Zaharia

    2003-10-20

    Based on the ideal-MHD model the stability of ballooning modes is investigated by employing realistic 3D magnetospheric equilibria, in particular for the substorm growth phase. Previous MHD ballooning stability calculations making use of approximations on the plasma compressibility can give rise to erroneous conclusions. Our results show that without making approximations on the plasma compressibility the MHD ballooning modes are unstable for the entire plasma sheet where beta (sub)eq is greater than or equal to 1, and the most unstable modes are located in the strong cross-tail current sheet region in the near-Earth plasma sheet, which maps to the initial brightening location of the breakup arc in the ionosphere. However, the MHD beq threshold is too low in comparison with observations by AMPTE/CCE at X = -(8 - 9)R(sub)E, which show that a low-frequency instability is excited only when beq increases over 50. The difficulty is mitigated by considering the kinetic effects of ion gyrorad ii and trapped electron dynamics, which can greatly increase the stabilizing effects of field line tension and thus enhance the beta(sub)eq threshold [Cheng and Lui, 1998]. The consequence is to reduce the equatorial region of the unstable ballooning modes to the strong cross-tail current sheet region where the free energy associated with the plasma pressure gradient and magnetic field curvature is maximum.

  19. [The mechanism of vasculogenesis: the critical role of transforming growth factor-beta 1 in the formation of vessel-like structures during the differentiation in vitro of murine embryonic stem cells].

    PubMed

    Tsung, H C; Yao, Z

    1996-09-01

    When ES-5 cells were transfected with an exogenous porcine TGF-beta 1 gene, one can obtain clones of genetically modified ES cells with over-expression of the transfected gene. We called the genetically modified ES-5 cells as ES-T cells. When ES-T cells were used to study their differentiation in vitro by all trans-retinoic acid (RA), it was soon noticed that embryoid bodies of ES-T cells can exclusively differentiate into endothelial cells and vessel-like structures, but not in their parent ES-5 cells. The above result is the first indication that the differentiation of tubular structures in embryoid bodies of ES-T cells may somehow be related to TGF-beta 1. To demonstrate further the role of TGF-beta 1 in the formation of vessel-like structures, the cultured ES-5 cells in the presence of added rhTGF-beta 1 were closely followed in the course of their differentiation. We have, thus, demonstrated the promoting effects of exogenous rhTGF-beta 1 in the formation of vessel-like structures, morphologically similar to those structures derived from ES-T6 cells, during the differentiation of ES-5 cells, both in monolayer culture, in three dimensional collagen gel and in embryoid bodies cultured on gelatin-coated tissue culture wells. Addition of suitable amount of anti-TGF-beta 1 monoclonal antibody IgG (TB21) to the culture medium of embryoid bodies of ES-T6 cells could effectively abolish the formation of vessel-like structures induced by retinoic acid. The percentage of the inhibition was very high, giving a figure comparable to that of atypical vessel-like structures formed in the control embryoid bodies from their parent ES-5 cells. The flat epithelial-like cells and round cells differentiated from embryoid bodies of ES-T6 cells were stained rather strongly for laminin and type IV collagen by immunofluorescent procedure. The above results indicate clearly that TGF-beta 1 is a crucial factor in organizing the differentiated derivatives (endothelial-like cells and

  20. IO SUBSYSTEM 1 BETA

    SciTech Connect

    Sjaardema, Greg

    2002-08-21

    "IO Subsystem Ver. 1.0 Beta" uses standard object-oriented principles to minimize dependencies between the underlying input or output database format and the client code (i.e., Sierra) using the io subsystem. The interface and priciples are simolar to the Facade pattern described in the "Design Patterns" book by Gamma, et.al. The software uses data authentication algorithms to ensure data input/output is consistent with model being defined. "IO Subsystem Ver. 1.0 Beta" is a database independent input/output library for finite element analysis, preprocessing, post processing, and translation programs.

  1. Improving the medical 'take sheet'.

    PubMed

    Reed, Oliver

    2014-01-01

    The GMC states that "Trainees in hospital posts must have well organised handover arrangements, ensuring continuity of patient care[1]". In the Belfast City Hospital throughout the day there can be multiple new medical admissions. These can be via the GP Unit, transfers for tertiary care, and transfers due to bed shortages in other hospitals. Over the course of 24 hours there can be up to four medical SHOs and three registrars that fill in the take sheet. Due to the variety of admission routes and number of doctors looking after the medical take information can be lost during handover between SHOs. In the current format there is little room to write and key and relevant information on the medical take sheet about new and transferring patients. I felt that this handover sheet could be improved. An initial questionnaire demonstrated that 47% found the old proforma easy to use and 28.2% felt that it allowed them to identify sick patients. 100% of SHOs and Registrars surveyed felt that it could be improved from its current form. From feedback from my colleagues I created a new template and trialled it in the hospital. A repeat questionnaire demonstrated that 92.3% of responders felt the new format had improved medical handover and that 92.6% felt that it allowed safe handover most of the time/always. The success of this new proforma resulted in it being implemented on a permanent basis for new medical admissions and transfers to the hospital.

  2. Folding mechanisms of individual beta-hairpins in a Go model of Pin1 WW domain by all-atom molecular dynamics simulations.

    PubMed

    Luo, Zhonglin; Ding, Jiandong; Zhou, Yaoqi

    2008-06-14

    This paper examines the folding mechanism of an individual beta-hairpin in the presence of other hairpins by using an off-lattice model of a small triple-stranded antiparallel beta-sheet protein, Pin1 WW domain. The turn zipper model and the hydrophobic collapse model originally developed for a single beta-hairpin in literature is confirmed to be useful in describing beta-hairpins in model Pin1 WW domain. We find that the mechanism for folding a specific hairpin is independent of whether it folds first or second, but the formation process are significantly dependent on temperature. More specifically, beta1-beta2 hairpin folds via the turn zipper model at a low temperature and the hydrophobic collapse model at a high temperature, while the folding of beta2-beta3 hairpin follows the turn zipper model at both temperatures. The change in folding mechanisms is interpreted by the interplay between contact stability (enthalpy) and loop lengths (entropy), the effect of which is temperature dependent.

  3. 24 CFR 1710.117 - Cost sheet, signature of Senior Executive Officer.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 24 Housing and Urban Development 5 2011-04-01 2011-04-01 false Cost sheet, signature of Senior... REGISTRATION Reporting Requirements § 1710.117 Cost sheet, signature of Senior Executive Officer. (a) Cost sheet—Format. (1) The cost sheet shall be prepared in accordance with the following format and...

  4. Increase in the β-Sheet Character of an Amyloidogenic Peptide upon Adsorption onto Gold and Silver Surfaces.

    PubMed

    Soltani, Nima; Gholami, Mohammad Reza

    2017-03-03

    Fibrillation of amyloid beta (Aβ) peptide is the hallmark of Alzheimer's disease. Given that interactions at the bio-nano interface affect the fibrillation tendency of this peptide, an understanding of the interactions at Aβ peptide-inorganic surfaces on the microscopic level can help to determine the possible neurotoxicity of nanoparticles. Here, the interactions between a fibril-forming peptide, Aβ25-35 , and (111) and (100) facets of gold and silver surfaces have been studied by conducting atomistic molecular dynamics simulations. The obtained results indicate that the adsorption onto gold and silver surfaces force the peptide into the β-sheet-rich conformations, which is prone to aggregation, suggesting a new mechanism for the acceleration of fibril formation upon interaction with nanoparticles. To quantify the β-sheet content for a single peptide, a new metrics based on the Ramachandran probability distribution is introduced.

  5. Electron Diffraction Evidence for the Ordering of Excess Nickel Atoms by Relation to Stoichiometry in Nickel-Rich Beta'-Nial Formation of a Nickel-Aluminum (Ni2al) Superlattices

    NASA Technical Reports Server (NTRS)

    Reynaud, F.

    1988-01-01

    In electron diffraction patterns of nickel-rich beta-NiAl alloys, many anomalies are observed. One of these is the appearance of diffuse intensity maxima between the reflexions of the B2 structure. This is explained by the short-range ordering of the excess nickel atoms on the simple cubic sublattice occupied only by aluminum atoms in the stoichiometric, perfectly ordered NiAl alloy. After annealing Ni 37.5 atomic percent Al and Ni 37.75 atomic percent Al for 1 week at 300 and 400 C, the diffuse intensity maxima transformed into sharp superstructure reflexions. These reflexions are explained by the formation of the four possible variants of an ordered hexagonal superstructure corresponding to the Ni2Al composition. This structure is closely related to the Ni2Al3 structure (same space group) formed by the ordering of vacancies on the nickel sublattice in aluminum-rich beta-NiAl alloys.

  6. Fluctuation dynamics in reconnecting current sheets

    NASA Astrophysics Data System (ADS)

    von Stechow, Adrian; Grulke, Olaf; Ji, Hantao; Yamada, Masaaki; Klinger, Thomas

    2015-11-01

    During magnetic reconnection, a highly localized current sheet forms at the boundary between opposed magnetic fields. Its steep perpendicular gradients and fast parallel drifts can give rise to a range of instabilities which can contribute to the overall reconnection dynamics. In two complementary laboratory reconnection experiments, MRX (PPPL, Princeton) and VINETA.II (IPP, Greifswald, Germany), magnetic fluctuations are observed within the current sheet. Despite the large differences in geometries (toroidal vs. linear), plasma parameters (high vs. low beta) and magnetic configuration (low vs. high magnetic guide field), similar broadband fluctuation characteristics are observed in both experiments. These are identified as Whistler-like fluctuations in the lower hybrid frequency range that propagate along the current sheet in the electron drift direction. They are intrinsic to the localized current sheet and largely independent of the slower reconnection dynamics. This contribution characterizes these magnetic fluctuations within the wide parameter range accessible by both experiments. Specifically, the fluctuation spectra and wave dispersion are characterized with respect to the magnetic topology and plasma parameters of the reconnecting current sheet.

  7. Thermal denaturation of beta-galactosidase and of two site-specific mutants.

    PubMed

    Edwards, R A; Jacobson, A L; Huber, R E

    1990-12-11

    The thermal denaturation of wild-type beta-galactosidase and two beta-galactosidases with substitutions at the active site was studied by kinetics, differential scanning calorimetry, electrophoresis, molecular exclusion chromatography, and circular dichroism. From the results, a model is developed for thermal denaturation of beta-galactosidase which includes the reversible dissociation of ligands, reversible formation of an inactive tetramer, irreversible dissociation of the inactive tetramer to inactive monomers, and subsequent aggregation of inactive monomers to dimers and larger aggregates. Under some conditions, partial reversibility of the activity loss could be demonstrated, and several intermediates in the thermal denaturation process were trapped by quenching and observed by electrophoresis and molecular exclusion chromatography. The ligands Mg2+ and phenylethyl thio-beta-D-galactoside increase the stability of beta-galactosidase to heat denaturation by shifting the ligand binding equilibrium according to Le Chatelier's principle, thus decreasing the concentration of the ligand-free tetramer which can proceed to subsequent steps. Circular dichroism results indicated that beta-galactosidase is dominated by beta-sheet with lower amounts of alpha-helix. Large changes in secondary structure begin to occur only after activity has been lost. Single amino acid changes at the active site can have significant effects on thermal stability of beta-galactosidases. Some of the effects result from increased thermal stability of the ligand-free enzyme itself. Other effects result from changes in ligand binding, but the magnitude of the resulting changes in stability is not related to the strength of ligand binding in a simple fashion.

  8. Perforating Thin Metal Sheets

    NASA Technical Reports Server (NTRS)

    Davidson, M. E.

    1985-01-01

    Sheets only few mils thick bonded together, punched, then debonded. Three-step process yields perforated sheets of metal. (1): Individual sheets bonded together to form laminate. (2): laminate perforated in desired geometric pattern. (3): After baking, laminate separates into individual sheets. Developed for fabricating conductive layer on blankets that collect and remove ions; however, perforated foils have other applications - as conductive surfaces on insulating materials; stiffeners and conductors in plastic laminates; reflectors in antenna dishes; supports for thermal blankets; lightweight grille cover materials; and material for mockup of components.

  9. W-Band Sheet Beam Klystron Design

    SciTech Connect

    Scheitrum, G.; Caryotakis, G.; Burke, A.; Jensen, A.; Jongewaard, E.a Krasnykh, A.; Neubauer, M.; Phillips, R.; Rauenbuehler, K.; /SLAC

    2011-11-11

    Sheet beam devices provide important advantages for very high power, narrow bandwidth RF sources like accelerator klystrons [1]. Reduced current density and increased surface area result in increased power capabi1ity, reduced magnetic fields for focusing and reduced cathode loading. These advantages are offset by increased complexity, beam formation and transport issues and potential for mode competition in the ovennoded cavities and drift tube. This paper will describe the design issues encountered in developing a 100 kW peak and 2 kW average power sheet beam k1ystron at W-band including beam formation, beam transport, circuit design, circuit fabrication and mode competition.

  10. Gender-related effects of 17-{beta}-estradiol and B-hexachlorocyclohexane on liver tumor formation in medaka (Oryzias latipes)

    SciTech Connect

    Cooke, J.B.; Hinton, D.E.

    1994-12-31

    When medaka were acutely exposed to diethylnitrosamine (DEN), greater incidence of hepatocarcinoma was seen in female versus male fish. This is possibly related to elevated female endogenous estrogens, which increase liver weight and production of vitellogenin. To examine roles of estrogens in tumor modulation, 21-day old medaka were exposed to DEN (200 ppm for 24 hr.), then fed purified diets containing the estrogenic compound {beta}-hexachlorocyclohexane ({beta}-HCH) or 17-{beta}estradiol (E2) for 6 months. Incidences of basophilic preneoplastic foci of cellular alteration in females receiving DEN and 0.01, 0.1, or 1.0 ppm E2 were three times the incidences in similarly-treated males. Also, incidences of basophilic foci in DEN + 0.1 ppm E2 males were significantly increased over DEN-only males and were equal to incidences in DEN-only females. Liver weights and hepatosomatic indices of males given 0.1 ppm E2 were not significantly different than females fed control diet. Females fed 0.01-10.0 ppm {beta}-HCH after DEN had 4--5 times greater incidences of basophilic foci as males. Gender-related effects on kinetics of growth rates and volumes of foci are being examined.

  11. Minimalist design of water-soluble cross-[beta] architecture

    SciTech Connect

    Biancalana, Matthew; Makabe, Koki; Koide, Shohei

    2010-08-13

    Demonstrated successes of protein design and engineering suggest significant potential to produce diverse protein architectures and assemblies beyond those found in nature. Here, we describe a new class of synthetic protein architecture through the successful design and atomic structures of water-soluble cross-{beta} proteins. The cross-{beta} motif is formed from the lamination of successive {beta}-sheet layers, and it is abundantly observed in the core of insoluble amyloid fibrils associated with protein-misfolding diseases. Despite its prominence, cross-{beta} has been designed only in the context of insoluble aggregates of peptides or proteins. Cross-{beta}'s recalcitrance to protein engineering and conspicuous absence among the known atomic structures of natural proteins thus makes it a challenging target for design in a water-soluble form. Through comparative analysis of the cross-{beta} structures of fibril-forming peptides, we identified rows of hydrophobic residues ('ladders') running across {beta}-strands of each {beta}-sheet layer as a minimal component of the cross-{beta} motif. Grafting a single ladder of hydrophobic residues designed from the Alzheimer's amyloid-{beta} peptide onto a large {beta}-sheet protein formed a dimeric protein with a cross-{beta} architecture that remained water-soluble, as revealed by solution analysis and x-ray crystal structures. These results demonstrate that the cross-{beta} motif is a stable architecture in water-soluble polypeptides and can be readily designed. Our results provide a new route for accessing the cross-{beta} structure and expanding the scope of protein design.

  12. Mechanics of Sheeting Joints

    NASA Astrophysics Data System (ADS)

    Martel, S. J.

    2015-12-01

    Physical breakdown of rock across a broad scale spectrum involves fracturing. In many areas large fractures develop near the topographic surface, with sheeting joints being among the most impressive. Sheeting joints share many geometric, textural, and kinematic features with other joints (opening-mode fractures) but differ in that they are (a) discernibly curved, (b) open near the topographic surface, and (c) form subparallel to the topographic surface. Where sheeting joints are geologically young, the surface-parallel compressive stresses are typically several MPa or greater. Sheeting joints are best developed beneath domes, ridges, and saddles; they also are reported, albeit rarely, beneath valleys or bowls. A mechanism that accounts for all these associations has been sought for more than a century: neither erosion of overburden nor high lateral compressive stresses alone suffices. Sheeting joints are not accounted for by Mohr-Coulomb shear failure criteria. Principles of linear elastic fracture mechanics, together with the mechanical effect of a curved topographic surface, do provide a basis for understanding sheeting joint growth and the pattern sheeting joints form. Compressive stresses parallel to a singly or doubly convex topographic surface induce a tensile stress perpendicular to the surface at shallow depths; in some cases this alone could overcome the weight of overburden to open sheeting joints. If regional horizontal compressive stresses, augmented by thermal stresses, are an order of magnitude or so greater than a characteristic vertical stress that scales with topographic amplitude, then topographic stress perturbations can cause sheeting joints to open near the top of a ridge. This topographic effect can be augmented by pressure within sheeting joints arising from water, ice, or salt. Water pressure could be particularly important in helping drive sheeting joints downslope beneath valleys. Once sheeting joints have formed, the rock sheets between

  13. Regulatory roles of tumor necrosis factor-alpha and interleukin-1 beta in monocyte chemoattractant protein-1-mediated pulmonary granuloma formation in the rat.

    PubMed Central

    Flory, C. M.; Jones, M. L.; Miller, B. F.; Warren, J. S.

    1995-01-01

    Intravenous infusion of particulate yeast cell wall glucan into rats results in the synchronous development of angiocentric pulmonary granulomas that are composed almost entirely of monocytes and macrophages. Previous studies indicate that locally produced monocyte chemoattractant protein-1 (MCP-1) is required for full granuloma development. Because tumor necrosis factor-alpha (TNF-alpha) and interleukin 1 (IL-1) can induce MCP-1 production in a variety of cell types, we sought to determine their potential regulatory roles in this model. A single infusion of anti-TNF-alpha antibody at the time of glucan infusion (time 0) markedly reduced MCP-1 mRNA levels at 1 and 6 hours but not at later time points; there was no effect on granuloma size or number measured at 48 hours. When multiple infusions of anti-TNF-alpha antibody were administered over a 23-hour period (0 to 23 hours), MCP-1 mRNA was reduced through 24 hours, there was a significant reduction in peak bronchoalveolar lavage fluid MCP-1 activity at 48 hours, and there were marked reductions in granuloma size and number at 48 hours. Similar results were observed in animals that received infusions of anti-IL-1 beta. Infusion of anti-IL-1 beta at time 0 resulted in moderate reductions in MCP-1 mRNA at 1 and 6 hours and had no effect on granuloma size or number measured at 48 hours. When multiple infusions of anti-IL-1 beta were administered over a 23-hour period (0 to 23 hours), MCP-1 mRNA was reduced through 24 hours, there was a moderate reduction in peak bronchoalveolar lavage fluid MCP-1 activity at 48 hours, and there were marked reductions in granuloma size and number at 48 hours. A single infusion of anti-TNF-alpha and anti-IL-1 beta together at time 0 resulted in marked reductions in whole lung MCP-1 and mRNA at 1 and 6 hours, but not at 24 hours. Multiple combined infusions of anti-TNF-alpha and anti-IL-1 beta over a 23-hour period resulted in additive reductions in MCP-1 mRNA through 24 hours

  14. Sequence swapping does not result in conformation swapping for the beta4/beta5 and beta8/beta9 beta-hairpin turns in human acidic fibroblast growth factor.

    PubMed

    Kim, Jaewon; Lee, Jihun; Brych, Stephen R; Logan, Timothy M; Blaber, Michael

    2005-02-01

    The beta-turn is the most common type of nonrepetitive structure in globular proteins, comprising ~25% of all residues; however, a detailed understanding of effects of specific residues upon beta-turn stability and conformation is lacking. Human acidic fibroblast growth factor (FGF-1) is a member of the beta-trefoil superfold and contains a total of five beta-hairpin structures (antiparallel beta-sheets connected by a reverse turn). beta-Turns related by the characteristic threefold structural symmetry of this superfold exhibit different primary structures, and in some cases, different secondary structures. As such, they represent a useful system with which to study the role that turn sequences play in determining structure, stability, and folding of the protein. Two turns related by the threefold structural symmetry, the beta4/beta5 and beta8/beta9 turns, were subjected to both sequence-swapping and poly-glycine substitution mutations, and the effects upon stability, folding, and structure were investigated. In the wild-type protein these turns are of identical length, but exhibit different conformations. These conformations were observed to be retained during sequence-swapping and glycine substitution mutagenesis. The results indicate that the beta-turn structure at these positions is not determined by the turn sequence. Structural analysis suggests that residues flanking the turn are a primary structural determinant of the conformation within the turn.

  15. In-situ time-of-flight neutron diffraction of ErD2 (beta phase) formation during D2 loading.

    SciTech Connect

    Browning, James Frederick; Llobet, Anna; Snow, Clark Sheldon; Rodriguez, Mark Andrew; Wixom, Ryan R.

    2008-06-01

    In an effort to better understand the structural changes occurring during hydrogen loading of erbium target materials, we have performed D{sub 2} loading of erbium metal (powder) with simultaneous neutron diffraction analysis. This experiment tracked the conversion of Er metal to the {alpha} erbium deuteride (solid-solution) phase and then on to the {beta} (fluorite) phase. Complete conversion to ErD{sub 2.0} was accomplished at 10 Torr D{sub 2} pressure with deuterium fully occupying the tetrahedral sites in the fluorite lattice. Increased D{sub 2} pressure (up to 500 Torr at 450 C) revealed {approx}10 % deuterium occupation of the octahedral sites. Subsequent vacuum pumping of the sample at 450 C removed octahedral site occupancy while maintaining tetrahedral deuterium occupancy, thereby yielding stoichiometric ErD{sub 2.0} {beta} phase.

  16. Polyalanine and Abeta Aggregation Kinetics: Probing Intermediate Oligomer Formation and Structure Using Computer Simulations

    NASA Astrophysics Data System (ADS)

    Phelps, Erin Melissa

    2011-12-01

    The aggregation of proteins into stable, well-ordered structures known as amyloid fibrils has been associated with many neurodegenerative diseases. Amyloid fibrils are long straight, and un-branched structures containing several proto-filaments, each of which exhibits "cross beta structure," -- ribbon-like layers of large beta sheets whose strands run perpendicular to the fibril axis. It has been suggested in the literature that the pathway to fibril formation has the following steps: unfolded monomers associate into transient unstable oligomers, the oligomers undergo a rearrangement into the cross-beta structure and form into proto-filaments, these proto-filaments then associate and grow into fully formed fibrils. Recent experimental studies have determined that the unstable intermediate structures are toxic to cells and that their presence may play a key role in the pathogenesis of the amyloid diseases. Many efforts have been made to determine the structure of intermediate oligomer aggregates that form during the fibrillization process. The goal of this work is to provide details about the structure and formation kinetics of the unstable oligomers that appear in the fibril formation pathway. The specific aims of this work are to determine the steps in the fibril formation pathway and how the kinetics of fibrillization changes with variations in temperature and concentration. The method used is the application of discontinuous molecular dynamics to large systems of peptides represented with an intermediate resolution model, PRIME, that was previously developed in our group. Three different peptide sequences are simulated: polyalanine (KA14K), Abeta17-40, and Abeta17-42; the latter two are truncated sequences of the Alzheimer's peptide. We simulate the spontaneous assembly of these peptide chains from a random initial configuration of random coils. We investigate aggregation kinetics and oligomer formation of a system of 192 polyalanine (KA14K) chains over a

  17. Determination of isoprene and alpha-/beta-pinene oxidation products in boreal forest aerosols from Hyytiälä, Finland: diel variations and possible link with particle formation events.

    PubMed

    Kourtchev, I; Ruuskanen, T M; Keronen, P; Sogacheva, L; Dal Maso, M; Reissell, A; Chi, X; Vermeylen, R; Kulmala, M; Maenhaut, W; Claeys, M

    2008-01-01

    Biogenic volatile organic compounds (VOCs), such as isoprene and alpha-/beta-pinene, are photo-oxidized in the atmosphere to non-volatile species resulting in secondary organic aerosol (SOA). The goal of this study was to examine time trends and diel variations of oxidation products of isoprene and alpha-/beta-pinene in order to investigate whether they are linked with meteorological parameters or trace gases. Separate day-night aerosol samples (PM(1)) were collected in a Scots pine dominated forest in southern Finland during 28 July-11 August 2005 and analyzed with gas chromatography/mass spectrometry (GC/MS). In addition, inorganic trace gases (SO(2), CO, NO(x), and O(3)), meteorological parameters, and the particle number concentration were monitored. The median total concentration of terpenoic acids (i.e., pinic acid, norpinic acid, and two novel compounds, 3-hydroxyglutaric acid and 2-hydroxy-4-isopropyladipic acid) was 65 ng m(-3), while that of isoprene oxidation products (i.e., 2-methyltetrols and C(5) alkene triols) was 17.2 ng m(-3). The 2-methyltetrols exhibited day/night variations with maxima during day-time, while alpha-/beta-pinene oxidation products did not show any diel variation. The sampling period was marked by a relatively high condensation sink, caused by pre-existing aerosol particles, and no nucleation events. In general, the concentration trends of the SOA compounds reflected those of the inorganic trace gases, meteorological parameters, and condensation sink. Both the isoprene and alpha-/beta-pinene SOA products were strongly influenced by SO(2), which is consistent with earlier reports that acidity plays a role in SOA formation. The results support previous proposals that oxygenated VOCs contribute to particle growth processes above boreal forest.

  18. Formation of gamma(sup prime)-Ni3Al via the Peritectoid Reaction: gamma + beta (+ Al2O3)=gamma(sup prime)(+ Al2O3)

    NASA Technical Reports Server (NTRS)

    Copeland, Evan

    2008-01-01

    The activities of Al and Ni were measured using multi-cell Knudsen effusion-cell mass spectrometry (multi-cell KEMS), over the composition range 8-32 at.%Al and temperature range T=1400-1750 K in the Ni-Al-O system. These measurements establish that equilibrium solidification of gamma(sup prime)-Ni3Al-containing alloys occurs by the eutectic reaction, L (+ Al2O3)=gamma + Beta(+ Al2O3), at 1640 +/- 1 K and a liquid composition of 24.8 +/- 0.2 at.%al (at an unknown oxygen content). The {gamma + Beta (+Al2O3} phase field is stable over the temperature range 1633-1640 K, and gamma(sup prime)-Ni3Al forms via the peritectoid, gamma + Beta (+ Al2O3)=gamma(sup prime) (+ Al2O3), at 1633 +/- 1 K. This behavior is consistent with the current Ni-Al phase diagram and a new diagram is proposed. This new Ni-Al phase diagram explains a number of unusual steady-state solidification structures reported previously and provides a much simpler reaction scheme in the vicinity of the gamma(sup prime)-Ni2Al phase field.

  19. Formation of gamma'-Ni3Al via the Peritectoid Reaction: gamma plus beta (+Al2O3) equals gamma'(+Al2O3)

    NASA Technical Reports Server (NTRS)

    Copland, Evan

    2008-01-01

    The activities of Al and Ni were measured using multi-cell Knudsen effusion-cell mass spectrometry (multi-cell KEMS), over the composition range 8 - 32 at.%Al and temperature range T = 1400 - 1750 K in the Ni-Al-O system. These measurements establish that equilibrium solidification of gamma'-Ni3Al-containing alloys occurs by the eutectic reaction, L (+ Al2O3) = gamma + beta (+ Al2O3), at 1640 plus or minus 1 K and a liquid composition of 24.8 plus or minus 0.2 at.%Al (at an unknown oxygen content). The {gamma + beta + Al2O3} phase field is stable over the temperature range 1633 - 1640 K, and gamma'-Ni3Al forms via the peritectiod, gamma + beta (+ Al2O3) = gamma'(+ Al2O3), at 1633 plus or minus 1 K. This behavior is inconsistent with the current Ni-Al phase diagram and a new diagram is proposed. This new Ni-Al phase diagram explains a number of unusual steady state solidification structures reported previously and provides a much simpler reaction scheme in the vicinity of the gamma'-Ni3Al phase field.

  20. Current status of liquid sheet radiator research

    NASA Astrophysics Data System (ADS)

    Chubb, Donald L.; Calfo, Frederick D.; McMaster, Matthew S.

    1993-01-01

    Initial research on the external flow, low mass liquid sheet radiator (LSR), has been concentrated on understanding its fluid mechanics. The surface tension forces acting at the edges of the sheet produce a triangular planform for the radiating surface of width, W, and length, L. It has been experimentally verified that (exp L)/W agrees with the theoretical result, L/W = (We/8)exp 1/2, where We is the Weber number. Instability can cause holes to form in regions of large curvature such as where the edge cylinders join the sheet of thickness, tau. The W/tau limit that will cause hole formation with subsequent destruction of the sheet has yet to be reached experimentally. Although experimental measurements of sheet emissivity have not yet been performed because of limited program scope, calculations of the emissivity and sheet lifetime is determined by evaporation losses were made for two silicon based oils; Dow Corning 705 and Me(sub 2). Emissivities greater than 0.75 are calculated for tau greater than or equal to 200 microns for both oils. Lifetimes for Me(sub 2) are much longer than lifetimes for 705. Therefore, Me(sub 2) is the more attractive working fluid for higher temperatures (T greater than or equal to 400 K).

  1. Liquid sheet radiator

    NASA Technical Reports Server (NTRS)

    Chubb, Donald L.; White, K. Alan, III

    1987-01-01

    A new external flow radiator concept, the liquid sheet radiator (LSR), is introduced. The LSR sheet flow is described and an expression for the length/width (l/w), ratio is presented. A linear dependence of l/w on velocity is predicted that agrees with experimental results. Specific power for the LSR is calculated and is found to be nearly the same as the specific power of a liquid droplet radiator, (LDR). Several sheet thicknesses and widths were experimentally investigated. In no case was the flow found to be unstable.

  2. Microcomponent sheet architecture

    DOEpatents

    Wegeng, Robert S.; Drost, M. Kevin; McDonald, Carolyn E.

    1997-01-01

    The invention is a microcomponent sheet architecture wherein macroscale unit processes are performed by microscale components. The sheet architecture may be a single laminate with a plurality of separate microcomponent sections or the sheet architecture may be a plurality of laminates with one or more microcomponent sections on each laminate. Each microcomponent or plurality of like microcomponents perform at least one unit operation. A first laminate having a plurality of like first microcomponents is combined with at least a second laminate having a plurality of like second microcomponents thereby combining at least two unit operations to achieve a system operation.

  3. Microcomponent sheet architecture

    DOEpatents

    Wegeng, R.S.; Drost, M.K..; McDonald, C.E.

    1997-03-18

    The invention is a microcomponent sheet architecture wherein macroscale unit processes are performed by microscale components. The sheet architecture may be a single laminate with a plurality of separate microcomponent sections or the sheet architecture may be a plurality of laminates with one or more microcomponent sections on each laminate. Each microcomponent or plurality of like microcomponents perform at least one unit operation. A first laminate having a plurality of like first microcomponents is combined with at least a second laminate having a plurality of like second microcomponents thereby combining at least two unit operations to achieve a system operation. 14 figs.

  4. Silicon sheet technologies

    SciTech Connect

    Ciszek, T.F.

    1982-09-01

    A classification of silicon sheet growth methods by meniscus geometry permits them to be discussed in three groups: short meniscus techniques, high meniscus techniques, and extended meniscus or large solid/liquid interface area techniques. A second parameter, meniscus shaper interaction with the liquid silicon, is also instrumental in determining the characteristics of the various sheet processes. The current status of each process is discussed in the context of meniscus geometry and shaper/melt interaction. One aspect of sheet growth, surface area generation rate, is quantitatively compared with combined ingot growth and wafering surface area generation rates.

  5. Nuclear Data Sheets for A = 193

    SciTech Connect

    Achterberg, E.; Capurro, O.A.; Marti, G.V.; Vanin, V.R.; Castro, R.M.

    2006-01-15

    The present revision of the properties for the nuclides belonging to the A = 193 mass chain contains many improvements, corrections and additions to the material presented in previous evaluations (1998Ar07, Nucl. Data Sheets 83, 921 (1998); 1990Sh30, Nucl, Data Sheets 61, 519 (1990)). Among these are measurement results for quadrupole moments, angular distribution coefficients, half-lives and g-factors, for both previously known and new transitions and levels. In addition, major changes to the previously known status of this mass chain consist in the inclusion of data for new superdeformed bands in {sup 193}Pb, and the creation of level schemes for {sup 193}Bi, {sup 193}Po and {sup 193}At. The latter were previously unavailable, except for a very limited attempt in the case of {sup 193}Po, which was not confirmed in later work. Furthermore, the {sup 193}Os beta decay was re-evaluated in order to account for new absolute intensity measurements.

  6. Sepsis Fact Sheet

    MedlinePlus

    ... Remains Mysterious Life After Traumatic Injury: How the Body Responds Other NIGMS Fact Sheets Related Links Up to top This page last reviewed on February 01, 2017 Social Media Links Bookmark & Share Free Subscriptions Twitter Facebook YouTube ...

  7. Chlamydia - CDC Fact Sheet

    MedlinePlus

    Chlamydia – CDC Fact Sheet Chlamydia is a common sexually transmitted disease (STD) that can be easily cured. If left ... DSTDP) Centers for Disease Control and Prevention www. cdc. gov/ std CDC-INFO Contact Center 1-800- ...

  8. CMAQ Fact Sheet

    EPA Pesticide Factsheets

    For more than a decade, EPA and states have used EPA’s Community Multiscale Air Quality (CMAQ) Modeling System, a powerful computational tool for air quality management. Learn more about CMAQv5.2 by browsing our fact sheet.

  9. Avian Fact Sheet

    SciTech Connect

    NWCC Wildlife Work Group

    2004-12-01

    OAK-B135 After conducting four national research meetings, producing a document guiding research: Metrics and Methods for Determining or Monitoring Potential Impacts on Birds at Existing and Proposed Wind Energy Sites, 1999, and another paper, Avian Collisions with Wind Turbines: A Summary of Existing Studies and Comparisons to Other Sources of Avian Collision Mortality in the United States, 2001, the subcommittee recognized a need to summarize in a short fact sheet what is known about avian-wind interaction and what questions remain. This fact sheet attempts to summarize in lay terms the result of extensive discussion about avian-wind interaction on land. This fact sheet does not address research conducted on offshore development. This fact sheet is not intended as a conclusion on the subject; rather, it is a summary as of Fall/Winter 2002.

  10. Global ice sheet modeling

    SciTech Connect

    Hughes, T.J.; Fastook, J.L.

    1994-05-01

    The University of Maine conducted this study for Pacific Northwest Laboratory (PNL) as part of a global climate modeling task for site characterization of the potential nuclear waste respository site at Yucca Mountain, NV. The purpose of the study was to develop a global ice sheet dynamics model that will forecast the three-dimensional configuration of global ice sheets for specific climate change scenarios. The objective of the third (final) year of the work was to produce ice sheet data for glaciation scenarios covering the next 100,000 years. This was accomplished using both the map-plane and flowband solutions of our time-dependent, finite-element gridpoint model. The theory and equations used to develop the ice sheet models are presented. Three future scenarios were simulated by the model and results are discussed.

  11. Interhemispheric ice-sheet synchronicity during the last glacial maximum

    USGS Publications Warehouse

    Weber, M.E.; Clark, P.U.; Ricken, W.; Mitrovica, J.X.; Hostetler, S.W.; Kuhn, G.

    2011-01-01

    The timing of the last maximum extent of the Antarctic ice sheets relative to those in the Northern Hemisphere remains poorly understood. We develop a chronology for the Weddell Sea sector of the East Antarctic Ice Sheet that, combined with ages from other Antarctic ice-sheet sectors, indicates that the advance to and retreat from their maximum extent was within dating uncertainties synchronous with most sectors of Northern Hemisphere ice sheets. Surface climate forcing of Antarctic mass balance would probably cause an opposite response, whereby a warming climate would increase accumulation but not surface melting. Our new data support teleconnections involving sea-level forcing from Northern Hemisphere ice sheets and changes in North Atlantic deep-water formation and attendant heat flux to Antarctic grounding lines to synchronize the hemispheric ice sheets.

  12. Interhemispheric ice-sheet synchronicity during the Last Glacial Maximum.

    PubMed

    Weber, Michael E; Clark, Peter U; Ricken, Werner; Mitrovica, Jerry X; Hostetler, Steven W; Kuhn, Gerhard

    2011-12-02

    The timing of the last maximum extent of the Antarctic ice sheets relative to those in the Northern Hemisphere remains poorly understood. We develop a chronology for the Weddell Sea sector of the East Antarctic Ice Sheet that, combined with ages from other Antarctic ice-sheet sectors, indicates that the advance to and retreat from their maximum extent was within dating uncertainties synchronous with most sectors of Northern Hemisphere ice sheets. Surface climate forcing of Antarctic mass balance would probably cause an opposite response, whereby a warming climate would increase accumulation but not surface melting. Our new data support teleconnections involving sea-level forcing from Northern Hemisphere ice sheets and changes in North Atlantic deep-water formation and attendant heat flux to Antarctic grounding lines to synchronize the hemispheric ice sheets.

  13. Cosuppression of the alpha subunits of beta-conglycinin in transgenic soybean seeds induces the formation of endoplasmic reticulum-derived protein bodies.

    PubMed

    Kinney, A J; Jung, R; Herman, E M

    2001-05-01

    The expression of the alpha and alpha' subunits of beta-conglycinin was suppressed by sequence-mediated gene silencing in transgenic soybean seed. The resulting seeds had similar total oil and protein content and ratio compared with the parent line. The decrease in beta-conglycinin protein was apparently compensated by an increased accumulation of glycinin. In addition, proglycinin, the precursor of glycinin, was detected as a prominent polypeptide band in the protein profile of the transgenic seed extract. Electron microscopic analysis and immunocytochemistry of maturing transgenic soybean seeds indicated that the process of storage protein accumulation was altered in the transgenic line. In normal soybeans, the storage proteins are deposited in pre-existing vacuoles by Golgi-derived vesicles. In contrast, in transgenic seed with reduced beta-conglycinin levels, endoplasmic reticulum (ER)-derived vesicles were observed that resembled precursor accumulating-vesicles of pumpkin seeds and the protein bodies accumulated by cereal seeds. Their ER-derived membrane of the novel vesicles did not contain the protein storage vacuole tonoplast-specific protein alpha-TIP, and the sequestered polypeptides did not contain complex glycans, indicating a preGolgi and nonvacuolar nature. Glycinin was identified as a major component of these novel protein bodies and its diversion from normal storage protein trafficking appears to be related to the proglycinin buildup in the transgenic seed. The stable accumulation of proteins in a protein body compartment instead of vacuolar accumulation of proteins may provide an alternative intracellular site to sequester proteins when soybeans are used as protein factories.

  14. The iA{beta}5p {beta}-breaker peptide regulates the A{beta}(25-35) interaction with lipid bilayers through a cholesterol-mediated mechanism

    SciTech Connect

    Vitiello, Giuseppe; Grimaldi, Manuela; D'Ursi, Anna Maria; D'Errico, Gerardino

    2012-01-06

    Highlights: Black-Right-Pointing-Pointer iA{beta}5p shows a significant tendency to deeply penetrates the hydrophobic core of lipid membrane. Black-Right-Pointing-Pointer A{beta}(25-35) locates in the external region of the membrane causing a re-positioning of CHOL. Black-Right-Pointing-Pointer iA{beta}5p withholds cholesterol in the inner hydrophobic core of the lipid membrane. Black-Right-Pointing-Pointer iA{beta}5p prevents the A{beta}(25-35) release from the lipid membrane. -- Abstract: Alzheimer's disease is characterized by the deposition of aggregates of the {beta}-amyloid peptide (A{beta}) in the brain. A potential therapeutic strategy for Alzheimer's disease is the use of synthetic {beta}-sheet breaker peptides, which are capable of binding A{beta} but unable to become part of a {beta}-sheet structure, thus inhibiting the peptide aggregation. Many studies suggest that membranes play a key role in the A{beta} aggregation; consequently, it is strategic to investigate the interplay between {beta}-sheet breaker peptides and A{beta} in the presence of lipid bilayers. In this work, we focused on the effect of the {beta}-sheet breaker peptide acetyl-LPFFD-amide, iA{beta}5p, on the interaction of the A{beta}(25-35) fragment with lipid membranes, studied by Electron Spin Resonance spectroscopy, using spin-labeled membrane components (either phospholipids or cholesterol). The ESR results show that iA{beta}5p influences the A{beta}(25-35) interaction with the bilayer through a cholesterol-mediated mechanism: iA{beta}5p withholds cholesterol in the inner hydrophobic core of the bilayer, making the interfacial region more fluid and capable to accommodate A{beta}(25-35). As a consequence, iA{beta}5p prevents the A{beta}(25-35) release from the lipid membrane, which is the first step of the {beta}-amyloid aggregation process.

  15. Biodiesel Basics (Fact Sheet)

    SciTech Connect

    Not Available

    2014-06-01

    This fact sheet provides a brief introduction to biodiesel, including a discussion of biodiesel blends, which blends are best for which vehicles, where to buy biodiesel, how biodiesel compares to diesel fuel in terms of performance, how biodiesel performs in cold weather, whether biodiesel use will plug vehicle filters, how long-term biodiesel use may affect engines, biodiesel fuel standards, and whether biodiesel burns cleaner than diesel fuel. The fact sheet also dismisses the use of vegetable oil as a motor fuel.

  16. Energy information sheets

    SciTech Connect

    1995-07-01

    The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the public. The Energy Information Sheets was developed to provide general information on various aspects of fuel production, prices, consumption, and capability. Additional information on related subject matter can be found in other Energy Information Administration (EIA) publications as referenced at the end of each sheet.

  17. Beta measurements

    NASA Technical Reports Server (NTRS)

    Schotland, R. M.; Warren, A. J.; Funariu, O. M.

    1991-01-01

    The second year's results of the BETA project research are presented. The program is divided into two areas, aerosol modification and climatology in the trade wind region and the climatology of BETA (CO2) on remote mountain top locations. Limited data is available on the aerosol climatology of the marine free troposphere (MFT) in the trade wind region. In order to study the effects of cumulus convection on the MFT values of BETA, a cloud model was developed to simulate the evolution of a typical Pacific trade wind cumulus cloud. The stages involved in this development are outlined. The assembly of the major optical components of the lidar was made. Tests were run of the spectral bandwidth of the Synrad laser when a portion of the beam is mixed with a component which has traveled 450 meters corresponding to a delay of 1.5 microsecs. The bandwidth of the beat signal was measured to be 3 KHz. The data processing system based on a parallel processing filter bank analyzer using true time squaring detectors at each filter was completed.

  18. In-situ Pb isotope analysis of Fe-Ni-Cu sulphides by laser ablation multi-collector ICPMS: New insights into ore formation in the Sudbury impact melt sheet

    NASA Astrophysics Data System (ADS)

    Darling, J. R.; Storey, C. D.; Hawkesworth, C. J.; Lightfoot, P. C.

    2012-12-01

    Laser-ablation (LA) multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) is ideally suited to in situ determination of isotope ratios in sulphide minerals. Using samples of magmatic sulphide ore from the Sudbury impact structure, we test LA-MC-ICPMS analytical protocols that aim to meet a range of analytical challenges in the analysis of Pb isotopes. These include: potential matrix sensitive isotopic fractionation; interferences on Pb isotopes; low melting points of many sulphide minerals; the availability of standards. Magmatic sulphides of wide ranging mineralogy (pyrrhotite, pentlandite, chalcopyrite, pyrite and sphalerite) were analysed for Pb isotopic composition, using the silicate glass NIST SRM 610 as an external standard to correct for instrumental mass-fractionation. Despite matrix sensitive melting and re-deposition around ablation pits, several lines of evidence indicate that all analyses are accurate, within typical analytical uncertainties of 0.003-2% (2σ), and that the defined approach is insensitive to compositional diversity in sample matrix: (a) laser ablation and dissolution based measurements of sulphide powders are in agreement; (b) analyses from each sample define isochron ages within uncertainty of the known crystallization age (1850 Ma); (c) the results of sulphide measurements by laser ablation are consistent with age-corrected feldspar analyses from the same samples. The results have important implications for ore formation in Sudbury. The Pb isotope data regressions are consistent with age corrected feldspar analyses from each respective sample, which together with time integrated Th/U ratios that match whole rock values (3.1, 4.0 and 6.1 for the Worthington, Copper Cliff and Parkin Offset Dykes, respectively) indicate chemical equilibrium between the silicate and sulphide systems during ore formation. The sulphides within each respective sample have indistinguishable model initial Pb isotope ratios (207Pb/204Pbm

  19. Heterogeneity of the Pancreatic Beta Cell

    PubMed Central

    Gutierrez, Giselle Dominguez; Gromada, Jesper; Sussel, Lori

    2017-01-01

    The pancreatic beta cell functions as a key regulator of blood glucose levels by integrating a variety of signals in response to changing metabolic demands. Variations in beta cell identity that translate into functionally different subpopulations represent an interesting mechanism to allow beta cells to efficiently respond to diverse physiological and pathophysiological conditions. Recently, there is emerging evidence that morphological and functional differences between beta cells exist. Furthermore, the ability of novel single cell technologies to characterize the molecular identity of individual beta cells has created a new era in the beta cell field. These studies are providing important novel information about the origin of beta cell heterogeneity, the type and proportions of the different beta cell subpopulations, as well as their intrinsic properties. Furthermore, characterization of different beta cell subpopulations that could variably offer protection from or drive progression of diabetes has important clinical implications in diabetes prevention, beta cell regeneration and stem cell treatments. In this review, we will assess the evidence that supports the existence of heterogeneous populations of beta cells and the factors that could influence their formation. We will also address novel studies using islet single cell analysis that have provided important information toward understanding beta cell heterogeneity and discuss the caveats that may be associated with these new technologies. PMID:28321233

  20. Fiber formation of a synthetic spider peptide derived from Nephila clavata.

    PubMed

    Hidaka, Yuji; Kontani, Ko-Ichi; Taniguchi, Rina; Saiki, Masatoshi; Yokoi, Sayoko; Yukuhiro, Kenji; Yamaguchi, Hiroshi; Miyazawa, Mitsuhiro

    2011-01-01

    Dragline silk is a high-performance biopolymer with exceptional mechanical properties. Artificial spider dragline silk is currently prepared by a recombinant technique or chemical synthesis. However, the recombinant process is costly and large-sized synthetic peptides are needed for fiber formation. In addition, the silk fibers that are produced are much weaker than a fiber derived from a native spider. In this study, a small peptide was chemically synthesized and examined for its ability to participate in fiber formation. A short synthetic peptide derived from Nephila clavata was prepared by a solid-phase peptide method, based on a prediction using the hydrophobic parameter of each individual amino acid residue. After purification of the spider peptide, fiber formation was examined under several conditions. Fiber formation proceeded in the acidic pH range, and larger fibers were produced when organic solvents such as trifluoroethanol and acetonitrile were used at an acidic pH. Circular dichroism measurements of the spider peptide indicate that the peptide has a beta-sheet structure and that the formation of a beta-sheet structure is required for the spider peptide to undergo fiber formation.

  1. Effect of Strand Symmetry on the Nanostructure and Material Properties in Beta-Hairpin Peptide Hydrogels

    NASA Astrophysics Data System (ADS)

    Hule, Rohan; Pochan, Darrin; Nagarkar, Radhika; Schneider, Joel

    2007-03-01

    Hydrogels have been established as promising biomaterials for applications such as scaffolds for tissue engineering, controlled drug delivery and cell encapsulation. De novo designed beta hairpin peptides, capable of undergoing self assembly and hydrogel formation, were investigated that contain asymmetric beta strand arms surrounding a turn sequence. The stimuli responsive self assembly of the hydrogels occurs via an intramolecular folding and strand interdigitation mechanism. CD and FTIR indicate a beta sheet secondary structure. WAXS shows a fibril structure reminiscent of the cross beta spine. SANS has been employed to globally quantify the local structure as being rod-like. Modification of the strand registry results in fibrils with non-twisting, laminated vs. twisted nanostructure. Fibril dimensions as measured by TEM and AFM corroborate the interdigitated assembly. Bulk material properties of these hydrogels studied using oscillatory rheology vary significantly for the different morphologies. Differences in the peptide registry that drive hydrogel nanostructure and the consequent material properties can be potentially utilized for usage in specific biomaterial applications.

  2. Self-assembly of the beta2-microglobulin NHVTLSQ peptide using a coarse-grained protein model reveals a beta-barrel species.

    PubMed

    Song, Wei; Wei, Guanghong; Mousseau, Normand; Derreumaux, Philippe

    2008-04-10

    Although a wide variety of proteins can assemble into amyloid fibrils, the structure of the early oligomeric species on the aggregation pathways remains unknown at an atomic level of detail. In this paper we report, using molecular dynamics simulations with the OPEP coarse-grained force field, the free energy landscape of a tetramer and a heptamer of the beta2-microglobulin NHVTLSQ peptide. On the basis of a total of more than 17 ns trajectories started from various states, we find that both species are in equilibrium between amorphous and well-ordered aggregates with cross-beta-structure, a perpendicular bilayer beta-sheet, and, for the heptamer, six- or seven-stranded closed and open beta-barrels. Moreover, analysis of the heptamer trajectories shows that the perpendicular bilayer beta-sheet is one possible precursor of the beta-barrel, but that this barrel can also be formed from a twisted monolayer beta-sheet with successive addition of chains. Comparison with previous aggregation simulations and the fact that nature constructs transmembrane beta-sheet proteins with pores open the possibility that beta-barrels with small inner diameters may represent a common intermediate during the early steps of aggregation.

  3. Fluorescence correlation spectroscopy at the oil-water interface: hard disk diffusion behavior in dilute beta-lactoglobulin layers precedes monolayer formation.

    PubMed

    Donsmark, Jesper; Rischel, Christian

    2007-06-05

    We have performed a thorough characterization of fluorescence correlations spectroscopy (FCS) applied to oil-water interfaces of viscous oil droplets in aqueous solution, including numerical wave-optical calculations of the detection geometry and regularized multicomponent analysis of sample data. It is shown how significant errors in the estimation of the surface concentration can be avoided when FCS is applied to an interface region. We present data on the adsorption dynamics of beta-lactoglobulin (BLG), a well-studied model system. It is found that electrostatic repulsion slows the adsorption process and reduces the initial saturation density far below the monolayer concentration. During the first stages of adsorption, the diffusion coefficients of adsorbed protein closely follow the 2D hard disk model of Lahtinen et al.1 in response to increased surface concentration, which suggests that protein-protein interactions are limited to long-range Coulombic interactions at this stage.

  4. Relevance of organic farming and effect of climatological conditions on the formation of alpha-acids, beta-acids, desmethylxanthohumol, and xanthohumol in hop (Humulus lupulus L.).

    PubMed

    Keukeleire, Jelle De; Janssens, Ina; Heyerick, Arne; Ghekiere, Greet; Cambie, Joris; Roldan-Ruiz, Isabel; Bockstaele, Erik Van; Keukeleire, Denis De

    2007-01-10

    The concentrations of alpha-acids, beta-acids, desmethylxanthohumol, and xanthohumol were monitored in the hop varieties Admiral (A), Wye Challenger (WC), and First Gold (FG) during the harvest seasons of 2003 through 2005. Hops grown under an organic regimen were compared to plants grown conventionally in hop fields in close vicinity. The concentrations of the key compounds depended very much on climatological conditions showing, in general, highest levels in poorest weather conditions (2004). Of the three varieties studied, FG was the only one showing a clear trend for higher concentrations of secondary metabolites under organic growing conditions than under conventional farming conditions. Cultivation of A and WC seems to be very sensitive to climatic conditions and environmental stresses caused by pests and diseases, thereby leading to various results. WC proved to be a rich source of bioactive chalcones, particularly desmethylxanthohumol.

  5. Balance equations for triple-joint vortex-sheet structures

    NASA Astrophysics Data System (ADS)

    Xia, Xi; Mohseni, Kamran

    2016-11-01

    A vortex sheet is the limiting case for a viscous shear layer as the thickness approaches zero. Recently, vortex-sheet based flow models have been demonstrated to provide significant reduction for numerical simulations of viscous and inviscid flows. In such modeling approaches, a prominent phenomenon is the formation of a new vortex sheet from existing vortex sheets, thereby creating a triple-joint vortex-sheet structure. In this study, the formation of the new vortex sheet is analytically determined by applying conservation laws of mass and momentum to flow surrounding the entire triple-joint vortex-sheet structure, together with the boundary conditions specific to any application. As a result, a general condition is obtained to determine the angle, strength, and velocity of the new vortex sheet. This model is validated by simulating airfoils in steady and unsteady background flows and comparing the flow structures and force calculations with experimental data. While the performance of this model is demonstrated in this study for the vortex shedding problem at the trailing edge, its future applications could be extended to flow separation on a smooth surface and triple contact point of multi-phase flows.

  6. Energy information sheets

    SciTech Connect

    Not Available

    1993-12-02

    The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the general public. Written for the general public, the EIA publication Energy Information Sheets was developed to provide information on various aspects of fuel production, prices, consumption and capability. The information contained herein pertains to energy data as of December 1991. Additional information on related subject matter can be found in other EIA publications as referenced at the end of each sheet.

  7. Light sheet microscopy.

    PubMed

    Weber, Michael; Mickoleit, Michaela; Huisken, Jan

    2014-01-01

    This chapter introduces the concept of light sheet microscopy along with practical advice on how to design and build such an instrument. Selective plane illumination microscopy is presented as an alternative to confocal microscopy due to several superior features such as high-speed full-frame acquisition, minimal phototoxicity, and multiview sample rotation. Based on our experience over the last 10 years, we summarize the key concepts in light sheet microscopy, typical implementations, and successful applications. In particular, sample mounting for long time-lapse imaging and the resulting challenges in data processing are discussed in detail.

  8. Curved cap corrugated sheet

    NASA Technical Reports Server (NTRS)

    Davis, R. C.; Bales, T. T.; Royster, D. M.; Jackson, L. R. (Inventor)

    1984-01-01

    The report describes a structure for a strong, lightweight corrugated sheet. The sheet is planar or curved and includes a plurality of corrugation segments, each segment being comprised of a generally U-shaped corrugation with a part-cylindrical crown and cap strip, and straight side walls and with secondary corrugations oriented at right angles to said side walls. The cap strip is bonded to the crown and the longitudinal edge of said cap strip extends beyond edge at the intersection between said crown and said side walls. The high strength relative to weight of the structure makes it desirable for use in aircraft or spacecraft.

  9. Ellagic acid promotes A{beta}42 fibrillization and inhibits A{beta}42-induced neurotoxicity

    SciTech Connect

    Feng, Ying; Yang, Shi-gao; Du, Xue-ting; Zhang, Xi; Sun, Xiao-xia; Zhao, Min; Sun, Gui-yuan; Liu, Rui-tian

    2009-12-25

    Smaller, soluble oligomers of {beta}-amyloid (A{beta}) play a critical role in the pathogenesis of Alzheimer's disease (AD). Selective inhibition of A{beta} oligomer formation provides an optimum target for AD therapy. Some polyphenols have potent anti-amyloidogenic activities and protect against A{beta} neurotoxicity. Here, we tested the effects of ellagic acid (EA), a polyphenolic compound, on A{beta}42 aggregation and neurotoxicity in vitro. EA promoted A{beta} fibril formation and significant oligomer loss, contrary to previous results that polyphenols inhibited A{beta} aggregation. The results of transmission electron microscopy (TEM) and Western blot displayed more fibrils in A{beta}42 samples co-incubated with EA in earlier phases of aggregation. Consistent with the hypothesis that plaque formation may represent a protective mechanism in which the body sequesters toxic A{beta} aggregates to render them harmless, our MTT results showed that EA could significantly reduce A{beta}42-induced neurotoxicity toward SH-SY5Y cells. Taken together, our results suggest that EA, an active ingredient in many fruits and nuts, may have therapeutic potential in AD.

  10. Modeling of the texture transformation in a Ti-64 sheet after hot compression

    SciTech Connect

    Moustahfid, H.; Humbert, M.; Philippe, M.J.

    1997-09-01

    Their aim was to investigate the mechanism of variant selection occurring in the phase transformation of a Ti-64 sheet after compression. For that purpose, a Ti-64 alloy sheet was 38% plastically deformed by compression in the {beta} field at 1050 C. The ODF of the {beta} phase at high temperature was determined by an indirect method. Comparison between the experimental texture of the {alpha} phase at room temperature and a simulated texture calculated without variant selection from the high temperature {beta} texture indicated that the phase transformation by cooling occurred with variant selection. By simulating the texture change due to the {beta}-{alpha} transformation the authors showed that in a first approximation this variant selection can be related to the active slip systems involved in the plastic deformation of the {beta} matrix.

  11. 46. HANDRAILING, DETAILS TYPE 'B' (Sheet 12 of 14 sheets), ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    46. HANDRAILING, DETAILS TYPE 'B' (Sheet 12 of 14 sheets), April 5, 1932 - West End-North Side Bridge, Spanning Ohio River, approximately 1 mile downstream from confluence of Monongahela & Allegheny rivers, Pittsburgh, Allegheny County, PA

  12. 5. Historic American Buildings Survey Taken from drawing sheet, SHEET ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. Historic American Buildings Survey Taken from drawing sheet, SHEET #21, Showing the house as restored since Survey. (Dormer windows omitted as not authentic) - Samuel des Marest House, River Road, New Milford, Bergen County, NJ

  13. 71. PALMDALE WATER COMPANY, EASTWOOD MULTIPLEARCHED DAM: STRESS SHEET, SHEET ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    71. PALMDALE WATER COMPANY, EASTWOOD MULTIPLE-ARCHED DAM: STRESS SHEET, SHEET 3; DECEMBER 20, 1918. Littlerock Water District files. - Little Rock Creek Dam, Little Rock Creek, Littlerock, Los Angeles County, CA

  14. Surface Effects on Amyloid Fibril Formation

    NASA Astrophysics Data System (ADS)

    Moores, Brad; Simons, Janet; Leonenko, Zoya

    2009-03-01

    Amyloid fibrils are insoluble aggregates composed of proteins in beta-sheet conformation, which are implicated in at least 20 diseases for which no cure is currently available. Although fibril plaque formation is associated with biological membranes in vivo, most of earlier research on fibrillogenesis has been performed in a solution phase, in which only a protein-protein interactions are considered. On the other hand, the surface of plasma membrane could provide the environment in which amyloid forming proteins could cluster. In order to get an insight into the understanding of the effect of the surface of plasma membrane, and the surfaces in general, on amyloid fibril formation, we used Atomic force microscopy to study binding of amyloid beta 1-42 peptide and amyloid fibril formation on model surfaces, such as chemically modified positively charged, negatively charged and hydrophobic substrates. The results show that structure, size and amount of larger fibrils and smaller aggregates depend on the type of surface, and differ from aggregation observed in solution.

  15. Algal Biofuels Fact Sheet

    SciTech Connect

    2009-10-27

    This fact sheet provides information on algal biofuels, which are generating considerable interest around the world. They may represent a sustainable pathway for helping to meet the U.S. biofuel production targets set by the Energy Independence and Security Act of 2007.

  16. Ethanol Myths Fact Sheet

    SciTech Connect

    2009-10-27

    Ethanol is a clean, renewable fuel that is helping to reduce our nation’s dependence on oil and can offer additional economic and environmental benefits in the future. This fact sheet is intended to address some common misconceptions about this important alternative fuel.

  17. Quick Information Sheets. 1988.

    ERIC Educational Resources Information Center

    Wisconsin Univ., Madison. Trace Center.

    The Trace Center gathers and organizes information on communication, control, and computer access for handicapped individuals. The information is disseminated in the form of brief sheets describing print, nonprint, and organizational resources and listing addresses and telephone numbers for ordering or for additional information. This compilation…

  18. Quick Information Sheets.

    ERIC Educational Resources Information Center

    Wisconsin Univ., Madison. Trace Center.

    This compilation of "Trace Quick Sheets" provides descriptions, prices, and ordering information for products and services that assist with communication, control, and computer access for disabled individuals. Product descriptions or product sources are included for: adaptive toys and toy modifications; head pointers, light pointers, and…

  19. Insulation Fact Sheet.

    ERIC Educational Resources Information Center

    Conservation and Renewable Energy Inquiry and Referral Service (DOE), Silver Spring, MD.

    Heating and cooling account for 50-70% of the energy consumed in the average American home. Heating water accounts for another 20%. A poorly insulated home loses much of this energy, causing drafty rooms and high energy bills. This fact sheet discusses how to determine if your home needs more insulation, the additional thermal resistance (called…

  20. GED Testing Fact Sheet

    ERIC Educational Resources Information Center

    GED Testing Service, 2009

    2009-01-01

    This GED Testing fact sheet provides information on: (1) GED[R] Tests; (2) Versions and Editions of the GED Tests; (3) Earning a Credential; (4) GED Testing Service[R]; (5) History of the GED Tests; (6) Who Accepts the GED Credential; (7) Public/Private Partnership of GEDTS; (8) Renowned GED Credential Recipients; (9) GED Testing Numbers for 2008;…

  1. Youth Demographics. Fact Sheet

    ERIC Educational Resources Information Center

    Lopez, Mark Hugo; Marcelo, Karlo Barrios

    2006-01-01

    This fact sheet compares the numbers of 18-25 year-old residents and citizens by gender, race, ethnicity, geographic distribution, marital status, military status, unemployment, educational attainment, and assesses population trends from 1968-2006. It explores such demographic characteristics of young people using data from the March Annual…

  2. Ethanol Basics (Fact Sheet)

    SciTech Connect

    Not Available

    2015-01-01

    Ethanol is a widely-used, domestically-produced renewable fuel made from corn and other plant materials. More than 96% of gasoline sold in the United States contains ethanol. Learn more about this alternative fuel in the Ethanol Basics Fact Sheet, produced by the U.S. Department of Energy's Clean Cities program.

  3. Effects of electron pressure anisotropy on current sheet configuration

    NASA Astrophysics Data System (ADS)

    Artemyev, A. V.; Vasko, I. Y.; Angelopoulos, V.; Runov, A.

    2016-09-01

    Recent spacecraft observations in the Earth's magnetosphere have demonstrated that the magnetotail current sheet can be supported by currents of anisotropic electron population. Strong electron currents are responsible for the formation of very thin (intense) current sheets playing the crucial role in stability of the Earth's magnetotail. We explore the properties of such thin current sheets with hot isotropic ions and cold anisotropic electrons. Decoupling of the motions of ions and electrons results in the generation of a polarization electric field. The distribution of the corresponding scalar potential is derived from the electron pressure balance and the quasi-neutrality condition. We find that electron pressure anisotropy is partially balanced by a field-aligned component of this polarization electric field. We propose a 2D model that describes a thin current sheet supported by currents of anisotropic electrons embedded in an ion-dominated current sheet. Current density profiles in our model agree well with THEMIS observations in the Earth's magnetotail.

  4. Fast Light-Sheet Scanner

    NASA Technical Reports Server (NTRS)

    Hunter, William W., Jr.; Humphreys, William M., Jr.; Bartram, Scott M.

    1995-01-01

    Optomechanical apparatus maintains sheet of pulsed laser light perpendicular to reference axis while causing sheet of light to translate in oscillatory fashion along reference axis. Produces illumination for laser velocimeter in which submicrometer particles entrained in flow illuminated and imaged in parallel planes displaced from each other in rapid succession. Selected frequency of oscillation range upward from tens of hertz. Rotating window continuously shifts sheet of light laterally while maintaining sheet parallel to same plane.

  5. Solar wind double ions beams and the heliospheric current sheet

    NASA Technical Reports Server (NTRS)

    Hammond, C. M.; Feldman, W. C.; Phillips, J. L.; Goldstein, B. E.; Balogh, A.

    1995-01-01

    Double ion beams are often observed in the solar wind, but little work has been done in relating these beams to structures within the solar wind. Double ion beams are observed as beams of a given ion species and charge state occurring at two different energies. We use the three-dimensional ion plasma instrument on board the Ulysses spacecraft to look for evidence of such beams associated with the heliospheric current sheet. In a subset chosen independently of plasma parameters consisting of 8 of cover 47 crossings of the current sheet made during the inecliptic phase of the Ulysses mission we find that these double ion beams are always present on either side of the current sheet. The double beams are present in both the proton and helium species. The secondary beam typically has a higher helium abundance, which suggests that these beams are formed in the helium-rich corona rather than in interplanetary space. The double beams are not present in the interior of the current sheet. Neither collisions nor effects of plasma beta can account for the disappearance of the double beams inside the current sheet in all eight cases. We postulate that these beams are formed by reconnection occurring near the Sun in the boundary region between the open field lines of the coronal holes and the closed field line region of the heliospheric current sheet. Such a scenario would be consistent with previous X ray measurements which suggect that reconnection is occurring in this region.

  6. Skill Sheets for Agricultural Mechanics.

    ERIC Educational Resources Information Center

    Iowa State Univ. of Science and Technology, Ames. Dept. of Agricultural Education.

    This set of 33 skill sheets for agricultural mechanics was developed for use in high school and vocational school agricultural mechanics programs. Some sheets teach operational procedures while others are for simple projects. Each skill sheet covers a single topic and includes: (1) a diagram, (2) a step-by-step construction or operational…

  7. Fact Sheets on Selected Programs.

    ERIC Educational Resources Information Center

    Administration for Children and Families (DHHS), Washington, DC.

    This paper provides 1- to 6-page fact sheets on 15 programs administered by the U.S. Department of Health and Human Services' Administration for Children and Families. Each fact sheet provides information on program services and funding. The fact sheets cover the following programs: Youth Gang Drug Prevention, Refugee Assistance, Runaway and…

  8. The Physics of Ice Sheets

    ERIC Educational Resources Information Center

    Bassis, J. N.

    2008-01-01

    The great ice sheets in Antarctica and Greenland are vast deposits of frozen freshwater that contain enough to raise sea level by approximately 70 m if they were to completely melt. Because of the potentially catastrophic impact that ice sheets can have, it is important that we understand how ice sheets have responded to past climate changes and…

  9. Beginning Child Care Fact Sheets.

    ERIC Educational Resources Information Center

    Tweedie, Pat

    These six fact sheets from Child Care Aware are designed to help parents ease their children's transition to child care. The first fact sheet, "Before Your Child's First Day," discusses tips such as: (1) "prepare your child"; (2) read and look at picture books about child care; and (3) "prepare yourself." The second fact sheet, "First Day Tips,"…

  10. Oligomerization of beta-amyloid of the Alzheimer's and the Dutch-cerebral-haemorrhage types.

    PubMed Central

    Sian, A K; Frears, E R; El-Agnaf, O M; Patel, B P; Manca, M F; Siligardi, G; Hussain, R; Austen, B M

    2000-01-01

    A novel ELISA has been developed which detects oligomerization of beta-amyloid (A beta). Oligomerization, fibrillization and neurotoxicity of native A beta associated with Alzheimer's disease (AD) type has been compared with E22Q A beta (amyloid beta-protein containing residues 1--40 with the native Glu at residue 22 changed to Gln) implicated in Dutch cerebral haemorrhage disease. Solutions of A beta rapidly yield soluble oligomers in a concentration-dependent manner, which are detected by the ELISA, and by size-exclusion gel chromatography. Conformational changes from disordered to beta-sheet occur more slowly than oligomerization, and fibrils are produced after prolonged incubation. The E22Q A beta oligomerizes, changes conformation and fibrillizes more rapidly than the native form and produces shorter stubbier fibrils. Aged fibrillar preparations of E22Q A beta are more potent than aged fibrils of native A beta in inducing apoptotic changes and toxic responses in human neuroblastoma cell lines, whereas low-molecular-mass oligomers in briefly incubated solutions are much less potent. The differences in the rates of oligomerization of the two A beta forms, their conformational behaviour over a range of pH values, and NMR data reported elsewhere, are consistent with a molecular model of oligomerization in which strands of A beta monomers initially overcome charge repulsion to form dimers in parallel beta-sheet arrangement, stabilized by intramolecular hydrophobic interactions, with amino acids of adjacent chains in register. PMID:10861242

  11. Interhemispheric ice-sheet synchronicity during the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Weber, M. E.; Clark, P. U.; Ricken, W.; Mitrovica, J. X.; Hostetler, S. W.; Kuhn, G.

    2012-04-01

    The timing of the last maximum extent of the Antarctic ice sheets relative to those in the Northern Hemisphere remains poorly understood because only a few findings with robust chronologies exist for Antarctic ice sheets. We developed a chronology for the Weddell Sea sector of the East Antarctic ice sheet that, combined with ages from other Antarctic ice-sheet sectors, indicates the advance to their maximum extent at 29 -28 ka, and retreat from their maximum extent at 19 ka was nearly synchronous with Northern Hemisphere ice sheets (Weber, M.E., Clark, P. U., Ricken, W., Mitrovica, J. X., Hostetler, S. W., and Kuhn, G. (2011): Interhemispheric ice-sheet synchronicity during the Last Glacial Maximum. - Science, 334, 1265-1269, doi: 10.1126:science.1209299). As for the deglaciation, modeling studies suggest a late ice-sheet retreat starting around 14 ka BP and ending around 7 ka BP with a large impact of an unstable West Antarctic Ice Sheet (WAIS) and a small impact of a stable East Antarctic Ice Sheet (EAIS). However, the Weddell Sea sites studied here, as well as sites from the Scotia Sea, provide evidence that specifically the EAIS responded much earlier, possibly provided a significant contribution to the last sea-level rise, and was much more dynamic than previously thought. Using the results of an atmospheric general circulation we conclude that surface climate forcing of Antarctic ice mass balance would likely cause an opposite response, whereby a warming climate would increase accumulation but not surface melting. Furthermore, our new data support teleconnections involving a sea-level fingerprint forced from Northern Hemisphere ice sheets as indicated by gravitational modeling. Also, changes in North Atlantic Deepwater formation and attendant heat flux to Antarctic grounding lines may have contributed to synchronizing the hemispheric ice sheets.

  12. Current status of solar cell performance of unconventional silicon sheets

    NASA Technical Reports Server (NTRS)

    Yoo, H. I.; Liu, J. K.

    1981-01-01

    It is pointed out that activities in recent years directed towards reduction in the cost of silicon solar cells for terrestrial photovoltaic applications have resulted in impressive advancements in the area of silicon sheet formation from melt. The techniques used in the process of sheet formation can be divided into two general categories. All approaches in one category require subsequent ingot wavering. The various procedures of the second category produce silicon in sheet form. The performance of baseline solar cells is discussed. The baseline process included identification marking, slicing to size, and surface treatment (etch-polishing) when needed. Attention is also given to the performance of cells with process variations, and the effects of sheet quality on performance and processing.

  13. Characteristics of liquid sheets formed by splash plate nozzles

    NASA Astrophysics Data System (ADS)

    Ahmed, M.; Amighi, A.; Ashgriz, N.; Tran, H. N.

    2008-01-01

    An experimental study was conducted to identify the effect of viscosity on the characteristics of liquid sheets formed by a splash plate nozzle. Various mixtures of corn syrup and water are used to obtain viscosities in the range 1-170 mPa.s. Four different splash plates with nozzle diameters of 0.5, 0.75, 1, and 2 mm, with a constant plate angle of 55° were tested. Liquid sheets formed under various operating conditions were directly visualized. The sheet atomization process for the range of parameters studied here is governed by two different mechanisms: Rayleigh-Plateau (R-P) and Rayleigh-Taylor (R-T) instabilities. R-P occurs at the rim and R-T occurs on the thin sheet. The rim instability can be laminar or turbulent, depending on the jet Reynolds number. The R-T instability of the sheet is observed at the outer edges of the radially spreading sheet, where the sheet is the thinnest. It can also occur inside the sheet, due to formation of holes and ruptures.

  14. Numerical simulation and fabrication of silicon sheet via spin casting.

    PubMed

    Lee, Jaewoo; Kim, Hyunhui; Lee, Changbum; Kim, Joonsoo; Jang, Bo-Yun; Lee, Jinseok; Ahn, Youngsoo; Yoon, Wooyoung

    2013-05-01

    A spin-casting process for fabricating polycrystalline silicon sheets for use as solar cell wafers is proposed, and the parameters that control the sheet thickness are investigated. A numerical study of the fluidity of molten silicon indicates that the formation of thin silicon sheets without a mold and via spin casting is feasible. The faster the rotation speed of graphite mold, the thinner the thickness of sheet. After the spread of the molten silicon to cover the graphite mold with rotation speed of above 500 rpm, the solidification has to start. Silicon sheets can be produced by using the centrifugal force under appropriate experimental conditions. The spin-cast sheet had a vertical columnar microstructure due to the normal heat extraction to the substrate, and the sheet lifetime varied from 0.1 microS to 0.3 microS measured by using the microwave photoconductance decay (MW-PCD) to confirm that the spin-cast silicon sheet is applicable to photovoltaics.

  15. Origami folding of polymer sheets by inkjet printing

    NASA Astrophysics Data System (ADS)

    Liu, Ying; Shaw, Brandi; Dickey, Michael D.; Genzer, Jan

    2015-03-01

    In analogy to the ancient Japanese art of paper folding (Origami), self-folding is an attractive strategy to induce the formation of three-dimensional (3D) objects with well-defined shapes and dimensions using conventional two-dimensional (2D) patterning techniques, such as lithography and inkjet printing. Self-folding can be applied in the areas of reconfigurable devices, actuators, and sensors. Here we demonstrate a simple method for self-folding of polymer sheets utilizing localized light absorption on selected areas of the pre-strained polymer sheet. The ink is patterned via a desktop printer and it defines the location of the `hinge' on the sheet. The inked areas on the 2D sheet absorb light preferentially, thus causing the polymer sheet to fold locally in the inked areas. The temperature gradients through the depth of the sheet induce localized shrinkage and the sheet folds within seconds. This patterned polymer sheets act as shape memory materials which can be programmed to fold into various 3D structures based on the nature of the light source, the shape and size of the ink patterns, and ink property. By controlling the aforementioned parameters we achieve a complete control of the time and degree of folding, which ultimately govern the final 3D shape of the folded object.

  16. Effect of the phospholipid chain length and head group on beta-phase formation of poly(9,9-dioctylfluorene) enclosed in liposomes.

    PubMed

    Tapia, María J; Monteserín, María; Burrows, Hugh D; Seixas de Melo, João S; Estelrich, Joan

    2013-01-01

    We have studied the effect of head group and alkyl chain length on β-phase formation in poly(9,9-dioctylfluorene) (PFO) solubilized in phospholipid liposomes. Systems studied have three different alkyl chain lengths (1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine [DMPC], 1,2-didodecanoyl-sn-glycero-3-phosphatidylcholine [DLPC], 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine [DPPC]) and head groups (1,2-dimyristoyl-sn-glycero-3-phosphate monosodium salt [DMPA], 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine [DMPE] and 1,2-dimyristoyl-sn-glycero-3-phospho-l-serine sodium salt [DMPS]). Changes in liposome size upon addition of PFO are followed by dynamic light scattering. All the phospholipids induce the formation of PFO β-phase, which is followed by the emission intensity and deconvolution of the absorption spectra. Both the head group and alkyl chain length affect the yield of β-phase. The photophysics of PFO incorporated in liposomes is characterized by stationary and time-resolved fluorescence, whereas the polymer-phospholipid interactions have been studied by the effect of the PFO concentration on the phospholipid phase transitions (differential scanning calorimetry [DSC]).

  17. Raman and AFM study of gamma irradiated plastic bottle sheets

    NASA Astrophysics Data System (ADS)

    Ali, Yasir; Kumar, Vijay; Sonkawade, R. G.; Dhaliwal, A. S.

    2013-02-01

    In this investigation, the effects of gamma irradiation on the structural properties of plastic bottle sheet are studied. The Plastic sheets were exposed with 1.25MeV 60Co gamma rays source at various dose levels within the range from 0-670 kGy. The induced modifications were followed by micro-Raman and atomic force microscopy (AFM). The Raman spectrum shows the decrease in Raman intensity and formation of unsaturated bonds with an increase in the gamma dose. AFM image displays rough surface morphology after irradiation. The detailed Raman analysis of plastic bottle sheets is presented here, and the results are correlated with the AFM observations.

  18. SHEET PLASMA DEVICE

    DOEpatents

    Henderson, O.A.

    1962-07-17

    An ion-electron plasma heating apparatus of the pinch tube class was developed wherein a plasma is formed by an intense arc discharge through a gas and is radially constricted by the magnetic field of the discharge. To avoid kink and interchange instabilities which can disrupt a conventional arc shortiy after it is formed, the apparatus is a pinch tube with a flat configuration for forming a sheet of plasma between two conductive plates disposed parallel and adjacent to the plasma sheet. Kink instabilities are suppressed by image currents induced in the conductive plates while the interchange instabilities are neutrally stable because of the flat plasma configuration wherein such instabilities may occur but do not dynamically increase in amplitude. (AEC)

  19. Ovine colostrum nanopeptide affects amyloid beta aggregation.

    PubMed

    Janusz, Maria; Woszczyna, Mirosław; Lisowski, Marek; Kubis, Adriana; Macała, Józefa; Gotszalk, Teodor; Lisowski, Józef

    2009-01-05

    A colostral proline-rich polypeptide complex (PRP) consisting of over 30 peptides shows beneficial effects in Alzheimer's disease (AD) patients when administered in the form of sublinqual tablets called Colostrinin. The aim of the present studies was to investigate whether nanopeptide fragment of PRP (NP) - one of the PRP complex components can affect aggregation of amyloid beta (Abeta1-42). The effect of NP on Abeta aggregation was studied using Thioflavin T (ThT) binding, atomic force microscopy, and analyzing circular dichroism spectra. Results presented suggest that NP can directly interact with amyloid beta, inhibit its aggregation and disrupt existing aggregates acting as a beta sheet breaker and reduce toxicity induced by aggregated forms of Abeta.

  20. Molecular characterization of alpha-keratins in comparison to associated beta-proteins in soft-shelled and hard-shelled turtles produced during the process of epidermal differentiation.

    PubMed

    Dalla Valle, L; Michieli, F; Benato, F; Skobo, T; Alibardi, L

    2013-11-01

    The tough corneous layer in the carapace and plastron of hard-shelled turtles derives from the accumulation of keratin-associated beta-proteins (KAbetaPs, formerly called beta-keratins) while these proteins are believed to be absent in soft-shelled turtles. Our bioinformatics and molecular study has instead shown that the epidermis of the soft-shelled turtle Apalone spinifera expresses beta-proteins like or even in higher amount than in the hard-shelled turtle Pseudemys nelsoni. The analysis of a carapace cDNAs library has allowed the identification and characterization of three alpha-keratins of type I and of ten beta-proteins (beta-keratins). The acidic alpha-keratins probably combine with the basic beta-proteins but the high production of beta-proteins in A. spinifera is not prevalent over that of alpha-keratin so that their combination does not determine the formation of hard corneous material. Furthermore the presence of a proline and cisteine in the beta-sheet region of beta-proteins in A. spinifera may be unsuited to form hard masses of corneous material. The higher amount of beta-proteins over alpha-keratins instead occurs in keratinocytes of the hard and inflexible epidermis of P. nelsoni determining the deposition of hard corneous material. The study suggests that the hardness of the corneous layer derives not exclusively from the interactions between alpha-keratins with KAbetaPs but also from the different dynamic of accumulation and loss of corneocytes in the corneous layer of the hard shelled turtles where a prevalent accumulation and piling of corneocytes takes place versus the soft shelled turtle where a rapid turnover of the stratum corneum occurs.

  1. Slow Mode Waves in the Heliospheric Plasma Sheet

    NASA Technical Reports Server (NTRS)

    Smith, Edward. J.; Zhou, Xiaoyan

    2007-01-01

    We report the results of a search for waves/turbulence in the Heliospheric Plasma Sheet (HPS) surrounding the Heliospheric Current Sheet (HCS). The HPS is treated as a distinctive heliospheric structure distinguished by relatively high Beta, slow speed plasma. The data used in the investigation are from a previously published study of the thicknesses of the HPS and HCS that were obtained in January to May 2004 when Ulysses was near aphelion at 5 AU. The advantage of using these data is that the HPS is thicker at large radial distances and the spacecraft spends longer intervals inside the plasma sheet. From the study of the magnetic field and solar wind velocity components, we conclude that, if Alfven waves are present, they are weak and are dominated by variations in the field magnitude, B, and solar wind density, NP, that are anti-correlated.

  2. Reducing slide sheet injury.

    PubMed

    Varcin-Coad, Lynn

    2008-12-01

    Slide sheets are often stated to be the cause of hand and forearm injuries. While there are many other possible reasons injuries to nursing staff, carer and client occur, the most important linking factors relating to musculoskeletal disorders and manual handling of people is the ongoing inappropriateness or lack of suitably designed and equipped work areas. As physiotherapist Lynn Varcin-Coad writes, staff are bearing the brunt of inefficiencies of design and lack of high order risk control.

  3. Clean Cities Fact Sheet

    SciTech Connect

    Not Available

    2004-01-01

    This fact sheet explains the Clean Cities Program and provides contact information for all coalitions and regional offices. It answers key questions such as: What is the Clean Cities Program? What are alternative fuels? How does the Clean Cities Program work? What sort of assistance does Clean Cities offer? What has Clean Cities accomplished? What is Clean Cities International? and Where can I find more information?

  4. Binding of cationic peptides (KX)4K to DPPG bilayers. Increasing the hydrophobicity of the uncharged amino acid X drives formation of membrane bound β-sheets: A DSC and FT-IR study.

    PubMed

    Hädicke, André; Blume, Alfred

    2016-06-01

    The binding of cationic peptides of the sequence (KX)4K to lipid vesicles of negatively charged dipalmitoyl-phosphatidylglycerol (DPPG) was investigated by differential scanning calorimetry (DSC) and temperature dependent Fourier-transformed infrared (FT-IR) spectroscopy. The hydrophobicity of the uncharged amino acid X was changed from G (glycine) over A (alanine), Abu (α-aminobutyric acid), V (valine) to L (leucine). The binding of the peptides caused an increase of the phase transition temperature (Tm) of DPPG by up to 20°C. The shift depended on the charge ratio and on the hydrophobicity of the amino acid X. Unexpectedly, the upward shift of Tm increased with increasing hydrophobicity of X. FT-IR spectroscopy showed a shift of the CH2 stretching vibrations of DPPG to lower frequency, particularly for bilayers in the liquid-crystalline phase, indicating an ordering of the hydrocarbon chains when the peptides were bound. Changes in the lipid C=O vibrational band indicated a dehydration of the lipid headgroup region after peptide binding. (KG)4K was bound in an unordered structure at all temperatures. All other peptides formed intermolecular antiparallel β-sheets, when bound to gel phase DPPG. However, for (KA)4K and (KAbu)4K, the β-sheets converted into an unordered structure above Tm. In contrast, the β-sheet structures of (KV)4K and (KL)4K remained stable even at 80°C when bound to the liquid-crystalline phase of DPPG. Strong aggregation of DPPG vesicles occurred after peptide binding. For the aggregates, we suggest a structure, where aggregated single β-sheets are sandwiched between opposing DPPG bilayers with a dehydrated interfacial region.

  5. Cereal beta-glucans

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cereal beta-glucans occur predominantly in oats and barley, but can be found in other cereals. Beta-glucan structure is a mixture of single beta-1,3-linkages and consecutive beta-1,4-linkages, and cellotriosyl and cellotetraosyl units typically make up 90-95% of entire molecule. Lichenase can hydr...

  6. Destabilization of 2D magnetic current sheets by resonance with bouncing electron - a new theory

    NASA Astrophysics Data System (ADS)

    Fruit, Gabriel; Louarn, Philippe; Tur, Anatoly

    2016-07-01

    In the general context of understanding the possible destabilization of the magnetotail before a substorm, we propose a kinetic model for electromagnetic instabilities in resonant interaction with trapped bouncing electrons. The geometry is clearly 2D and uses Harris sheet profile. Fruit et al. 2013 already used this model to investigate the possibilities of electrostatic instabilities. Tur et al. 2014 generalizes the model for full electromagnetic perturbations. Starting with a modified Harris sheet as equilibrium state, the linearized gyrokinetic Vlasov equation is solved for electromagnetic fluctuations with period of the order of the electron bounce period (a few seconds). The particle motion is restricted to its first Fourier component along the magnetic field and this allows the complete time integration of the non local perturbed distribution functions. The dispersion relation for electromagnetic modes is finally obtained through the quasi neutrality condition and the Ampere's law for the current density. The present talk will focus on the main results of this theory. The electrostatic version of the model may be applied to the near-Earth environment (8-12 R_{E}) where beta is rather low. It is showed that inclusion of bouncing electron motion may enhance strongly the growth rate of the classical drift wave instability. This model could thus explain the generation of strong parallel electric fields in the ionosphere and the formation of aurora beads with wavelength of a few hundreds of km. In the electromagnetic version, it is found that for mildly stretched current sheet (B_{z} > 0.1 B _{lobes}) undamped modes oscillate at typical electron bounce frequency with wavelength of the order of the plasma sheet thickness. As the stretching of the plasma sheet becomes more intense, the frequency of these normal modes decreases and beyond a certain threshold in B_{z}/B _{lobes}, the mode becomes explosive (pure imaginary frequency) with typical growing rate of a few

  7. Thymosin beta4: actin regulation and more.

    PubMed

    Yarmola, Elena G; Klimenko, Evguenia S; Fujita, Go; Bubb, Michael R

    2007-09-01

    The intracellular function of thymosin beta(4) is not limited to simple sequestration of globular actin. Our recent studies revealed that thymosin beta(4) affects actin critical concentration and forms a ternary complex with actin and profilin. The consequences of this complex formation can be very significant. Our new data demonstrate that it is likely that profilin affects binding of thymosin beta(4) to actin in the ternary complex through allosteric changes in actin rather than through competition for the binding site. The N- and C-terminal thymosin beta(4) helices are known to be unstructured in aqueous solution and to adopt helical conformation in organic solvents or upon binding to actin. Osmolytes stabilize protein structure, and TMAO (trimethylamine N-oxide) specifically stabilizes hydrogen bonds. This increases affinity of intact thymosin beta(4) to actin significantly, but the increase is much less for thymosin beta(4) sulfoxide. Our data show that oxidation does not alter binding of profilin to form a ternary complex, and therefore it is very likely that there is no direct steric interference by methionine 6 of thymosin beta(4). Rather, since TMAO has little effect on thymosin beta(4) sulfoxide, this observation is consistent with the hypothesis that methionine oxidation prevents helix transition. The experiment with truncated versions of thymosin beta(4) also supports this hypothesis. Oxidation and formation of the helices are important for both intra- and extracellular properties of thymosin beta(4). We found that actin and, in lesser extent, profilin-actin complex protect thymosin beta(4) from oxidation.

  8. Divergent effects of 17-{beta}-estradiol on human vascular smooth muscle and endothelial cell function diminishes TNF-{alpha}-induced neointima formation

    SciTech Connect

    Nintasen, Rungrat; Riches, Kirsten; Mughal, Romana S.; Viriyavejakul, Parnpen; Chaisri, Urai; Maneerat, Yaowapa; Turner, Neil A.; Porter, Karen E.

    2012-04-20

    Highlights: Black-Right-Pointing-Pointer TNF-{alpha} augments neointimal hyperplasia in human saphenous vein. Black-Right-Pointing-Pointer TNF-{alpha} induces detrimental effects on endothelial and smooth muscle cell function. Black-Right-Pointing-Pointer Estradiol exerts modulatory effects on TNF-induced vascular cell functions. Black-Right-Pointing-Pointer The modulatory effects of estradiol are discriminatory and cell-type specific. -- Abstract: Coronary heart disease (CHD) is a condition characterized by increased levels of proinflammatory cytokines, including tumor necrosis factor-{alpha} (TNF-{alpha}). TNF-{alpha} can induce vascular endothelial cell (EC) and smooth muscle cell (SMC) dysfunction, central events in development of neointimal lesions. The reduced incidence of CHD in young women is believed to be due to the protective effects of estradiol (E2). We therefore investigated the effects of TNF-{alpha} on human neointima formation and SMC/EC functions and any modulatory effects of E2. Saphenous vein (SV) segments were cultured in the presence of TNF-{alpha} (10 ng/ml), E2 (2.5 nM) or both in combination. Neointimal thickening was augmented by incubation with TNF-{alpha}, an effect that was abolished by co-culture with E2. TNF-{alpha} increased SV-SMC proliferation in a concentration-dependent manner that was optimal at 10 ng/ml (1.5-fold increase), and abolished by E2 at all concentrations studied (1-50 nM). Surprisingly, E2 itself at low concentrations (1 and 5 nM) stimulated SV-SMC proliferation to a level comparable to that of TNF-{alpha} alone. SV-EC migration was significantly impaired by TNF-{alpha} (42% of control), and co-culture with E2 partially restored the ability of SV-EC to migrate and repair the wound. In contrast, TNF-{alpha} increased SV-SMC migration by 1.7-fold, an effect that was completely reversed by co-incubation with E2. Finally, TNF-{alpha} potently induced ICAM-1 and VCAM-1 expression in both SV-EC and SV-SMC. However there

  9. Absorption of Beta Particles in Different Materials: An Undergraduate Experiment

    ERIC Educational Resources Information Center

    La Rocca, Paola; Riggi, Francesco

    2009-01-01

    The absorption of beta rays from a radioactive source in different materials was investigated by the use of a simple setup based on a Geiger counter and a set of absorber sheets. The number of electrons traversing the material was measured as a function of its thickness. Detailed GEANT simulations were carried out to reproduce the obtained…

  10. Dynamics of dikes versus cone sheets in volcanic systems

    NASA Astrophysics Data System (ADS)

    Galland, Olivier; Burchardt, Steffi; Hallot, Erwan; Mourgues, Régis; Bulois, Cédric

    2015-04-01

    Igneous sheet intrusions of various shapes, such as dikes and cone sheets, coexist as parts of complex volcanic plumbing systems likely fed by common sources. How they form is fundamental regarding volcanic hazards, but yet no dynamic model simulates and predicts satisfactorily their diversity. Here we present scaled laboratory experiments that reproduced dikes and cone sheets under controlled conditions (Galland et al., 2014). Our models show that their formation is governed by a dimensionless ratio (Π1), which describes the shape of the magma source, and a dynamic dimensionless ratio (Π2), which compares the viscous stresses in the flowing magma to the host-rock strength. Plotting our experiments against these two numbers results in a phase diagram evidencing a dike and a cone-sheet field, separated by a sharp transition that fits a power law. This result shows that dikes and cone sheets correspond to distinct physical regimes of magma emplacement in the crust. For a given host-rock strength, cone sheets preferentially form when the source is shallow, relative to its lateral extent, or when the magma influx velocity (or viscosity) is high. Conversely, dikes form when the source is deep compared to its size, or when magma influx rate (or viscosity) is low. Both dikes and cone sheets may form from the same source, the shift from one regime to the other being then controlled by magma dynamics, i.e., different values of Π2. The extrapolated empirical dike-to-cone sheet transition is in good agreement with the occurrence of dikes and cone sheets in various natural volcanic settings. Galland, O., Burchardt, S., Hallot, E., Mourgues, R., Bulois, C., 2014. Dynamics of dikes versus cone sheets in volcanic systems. Journal of Geophysical Research: Solid Earth, 2014JB011059, 10.1002/2014jb011059.

  11. beta1-integrin cytoplasmic subdomains involved in dominant negative function.

    PubMed

    Retta, S F; Balzac, F; Ferraris, P; Belkin, A M; Fässler, R; Humphries, M J; De Leo, G; Silengo, L; Tarone, G

    1998-04-01

    The beta1-integrin cytoplasmic domain consists of a membrane proximal subdomain common to the four known isoforms ("common" region) and a distal subdomain specific for each isoform ("variable" region). To investigate in detail the role of these subdomains in integrin-dependent cellular functions, we used beta1A and beta1B isoforms as well as four mutants lacking the entire cytoplasmic domain (beta1TR), the variable region (beta1COM), or the common region (beta1 deltaCOM-B and beta1 deltaCOM-A). By expressing these constructs in Chinese hamster ovary and beta1 integrin-deficient GD25 cells (Wennerberg et al., J Cell Biol 132, 227-238, 1996), we show that beta1B, beta1COM, beta1 deltaCOM-B, and beta1 deltaCOM-A molecules are unable to support efficient cell adhesion to matrix proteins. On exposure to Mn++ ions, however, beta1B, but none of the mutants, can mediate cell adhesion, indicating specific functional properties of this isoform. Analysis of adhesive functions of transfected cells shows that beta1B interferes in a dominant negative manner with beta1A and beta3/beta5 integrins in cell spreading, focal adhesion formation, focal adhesion kinase tyrosine phosphorylation, and fibronectin matrix assembly. None of the beta1 mutants tested shows this property, indicating that the dominant negative effect depends on the specific combination of common and B subdomains, rather than from the absence of the A subdomain in the beta1B isoform.

  12. Self-Assembly and Anti-Amyloid Cytotoxicity Activity of Amyloid beta Peptide Derivatives.

    PubMed

    Castelletto, V; Ryumin, P; Cramer, R; Hamley, I W; Taylor, M; Allsop, D; Reza, M; Ruokolainen, J; Arnold, T; Hermida-Merino, D; Garcia, C I; Leal, M C; Castaño, E

    2017-03-08

    The self-assembly of two derivatives of KLVFF, a fragment Aβ(16-20) of the amyloid beta (Aβ) peptide, is investigated and recovery of viability of neuroblastoma cells exposed to Aβ (1-42) is observed at sub-stoichiometric peptide concentrations. Fluorescence assays show that NH2-KLVFF-CONH2 undergoes hydrophobic collapse and amyloid formation at the same critical aggregation concentration (cac). In contrast, NH2-K(Boc)LVFF-CONH2 undergoes hydrophobic collapse at a low concentration, followed by amyloid formation at a higher cac. These findings are supported by the β-sheet features observed by FTIR. Electrospray ionization mass spectrometry indicates that NH2-K(Boc)LVFF-CONH2 forms a significant population of oligomeric species above the cac. Cryo-TEM, used together with SAXS to determine fibril dimensions, shows that the length and degree of twisting of peptide fibrils seem to be influenced by the net peptide charge. Grazing incidence X-ray scattering from thin peptide films shows features of β-sheet ordering for both peptides, along with evidence for lamellar ordering of NH2-KLVFF-CONH2. This work provides a comprehensive picture of the aggregation properties of these two KLVFF derivatives and shows their utility, in unaggregated form, in restoring the viability of neuroblastoma cells against Aβ-induced toxicity.

  13. Self-Assembly and Anti-Amyloid Cytotoxicity Activity of Amyloid beta Peptide Derivatives

    PubMed Central

    Castelletto, V.; Ryumin, P.; Cramer, R.; Hamley, I. W.; Taylor, M.; Allsop, D.; Reza, M.; Ruokolainen, J.; Arnold, T.; Hermida-Merino, D.; Garcia, C. I.; Leal, M. C.; Castaño, E.

    2017-01-01

    The self-assembly of two derivatives of KLVFF, a fragment Aβ(16–20) of the amyloid beta (Aβ) peptide, is investigated and recovery of viability of neuroblastoma cells exposed to Aβ (1–42) is observed at sub-stoichiometric peptide concentrations. Fluorescence assays show that NH2-KLVFF-CONH2 undergoes hydrophobic collapse and amyloid formation at the same critical aggregation concentration (cac). In contrast, NH2-K(Boc)LVFF-CONH2 undergoes hydrophobic collapse at a low concentration, followed by amyloid formation at a higher cac. These findings are supported by the β-sheet features observed by FTIR. Electrospray ionization mass spectrometry indicates that NH2-K(Boc)LVFF-CONH2 forms a significant population of oligomeric species above the cac. Cryo-TEM, used together with SAXS to determine fibril dimensions, shows that the length and degree of twisting of peptide fibrils seem to be influenced by the net peptide charge. Grazing incidence X-ray scattering from thin peptide films shows features of β-sheet ordering for both peptides, along with evidence for lamellar ordering of NH2-KLVFF-CONH2. This work provides a comprehensive picture of the aggregation properties of these two KLVFF derivatives and shows their utility, in unaggregated form, in restoring the viability of neuroblastoma cells against Aβ-induced toxicity. PMID:28272542

  14. Impact of different cultivation and induction regimes on the structure of cytosolic inclusion bodies of TEM1-beta-lactamase.

    PubMed

    Margreiter, Gerd; Schwanninger, Manfred; Bayer, Karl; Obinger, Christian

    2008-10-01

    The enzyme TEM1-beta-lactamase has been used as a model to study the impact of different cultivation and induction regimes on the structure of cytosolic inclusion bodies (IBs). The protein has been heterologously expressed in Escherichia coli in fed-batch cultivations at different temperatures (30, 37, and 40 degrees C) as well as induction regimes that guaranteed distinct product formation rates and ratios of soluble to aggregated protein. Additionally, shake flask cultivations at 20, 30, and 37 degrees C were performed. IBs were sampled during the whole bioprocess and structural analysis was performed by attenuated total reflectance Fourier transform infrared (ATR-FT-IR) spectroscopy. This work clearly demonstrates that the tested production regimes and rates had no impact on the IB structure, which was characterized by decreased alpha-helical and increased and modified beta-sheet contents compared to the native protein. Moreover, aggregates formed during refolding of IBs by solubilization and simple dilution showed very similar FT-IR spectra suggesting (i) the existence of only one critical folding step from which either aggregation (IB formation) or native folding branches off, and (ii) underlining the important role of the specific amino acid sequence in aggregation. The findings are discussed with respect to the known structure of TEM1-beta-lactamase and the reported kinetics of its (un)folding as well as contradictory data on the effect of cultivation regimes on IB structure(s) of other proteins.

  15. Luminescence Chronology for the Formation of Glacial Lake Calgary, Southern Alberta, Canada: Age Constraints for the Initiation of the Late Pleistocene Retreat of the Laurentide Ice Sheet from its Western Margin

    NASA Astrophysics Data System (ADS)

    Munyikwa, K.; Rittenour, T. M.

    2014-12-01

    Glacial Lake Calgary in southern Alberta, Canada, was a Late Pleistocene proglacial lake that formed along the southwest margin of the Laurentide Ice Sheet (LIS), dammed by the retreating ice sheet margin. Attempts to constrain the age of the lake using radiocarbon methods have been hampered by the lack of datable organic material. In an effort to apply an alternative chronometer, this study uses two optically stimulated luminescence (OSL) dating approaches to date fine grained sand and silt that were deposited in the lake during its existence. OSL dating determines the depositional ages of sediments by measuring the energy from ionizing radiation that is stored in mineral grains such as quartz and feldspar. Dividing the stored energy, also referred to as the paleodose, by the rate at which the dose accumulated, allows an age to be ascertained. In one method applied in this study, the paleodose stored in the feldspar component of the sediment is determined using normalized infrared stimulated luminescence signals acquired using a portable OSL reader. In the second method, blue optically stimulated luminescence signals obtained from quartz separates from the sediment by employing a regular OSL reader and standard protocols are used to determine the paleodose. After correcting the feldspar data for anomalous fading, the age results from the two dating approaches are compared. The ages signify a time period by which the LIS had retreated from the study area and, hence, serve as constraints for the initiation of the retreat of the ice sheet from its western limit. Advantages and limitations of the dating methods are briefly discussed. Constraining the chronology of the retreat of the LIS from western Canada allows for a better understanding of the driving forces behind ice sheet retreat. Secondly, assigning a temporal scale to the postglacial evolution of the environment of the region permits a better insight into the dynamics of the physical and biological

  16. The plasma sheet boundary layer

    NASA Technical Reports Server (NTRS)

    Eastman, T. E.; Frank, L. A.; Peterson, W. K.; Lennartsson, W.

    1984-01-01

    A spatially distinct, temporally variable, transition region between the magnetotail lobes and the central plasma sheet designated the plasma sheet boundary layer has been identified from a survey of particle spectra and three-dimensional distributions as sampled by the ISEE 1 LEPEDEA. The instrumentation and data presentation are described, and the signatures of the magnetotail plasma regimes are presented and discussed for the central plasma sheet and lobe and the plasma sheet boundary layer. Comparisons of plasma parameters and distribution fucntions are made and the evolution of ion velocity distributions within the plasma sheet boundary layer is discussed. The spatial distribution of the plasma sheet boundary layer is considered and ion composition measurements are presented.

  17. Effect of initial stagger selection on the handedness of Amyloid beta helical fibrils

    SciTech Connect

    Ghattyvenkatakrishna, Pavan K; Cheng, Xiaolin; Uberbacher, Edward C

    2013-01-01

    Various structural models for Amyloid $\\beta$ fibrils derived from a variety of experimental techniques are currently available. However, this data cannot differentiate between the relative position of the two arms of the $\\beta$ hairpin called the stagger. Amyloid fibrils of various heirarchical levels form left--handed helices composed of $\\beta$ sheets. However it is unclear if positive, negative and neutral staggers all form the macroscopic left--handed helices. Studying this is important since the success of computational approaches to develop drugs for amyloidic diseases will depend on selecting the physiologically relevant structure of the sheets. To address this issue we have conducted extensive molecular dynamics simulations of Amyloid$\\beta$ sheets of various staggers and show that only negative staggers generate the experimentally observed left--handed helices while positive staggers generate the incorrect right--handed helices. The implications of this result extend in to all amyloidic--aggregation type diseases.

  18. Low-Temperature Forming of Beta Titanium Alloys

    NASA Technical Reports Server (NTRS)

    Kaneko, R. S.; Woods, C. A.

    1983-01-01

    Low cost methods for titanium structural fabrication using advanced cold-formable beta alloys were investigated for application in a Mach 2.7 supersonic cruise vehicle. This work focuses on improving processing and structural efficiencies as compared with standard hot formed and riveted construction of alpha-beta alloy sheet structure. Mechanical property data and manufacturing parameters were developed for cold forming, brazing, welding, and processing Ti-15V-3Cr-3Sn-3Al sheet, and Ti-3Al-8V-6Cr-4Zr on a more limited basis. Cost and structural benefits were assessed through the fabrication and evaluation of large structural panels. The feasibility of increasing structural efficiency of beta titanium structure by selective reinforcement with metal matrix composite was also explored.

  19. Experimental realization of two-dimensional boron sheets.

    PubMed

    Feng, Baojie; Zhang, Jin; Zhong, Qing; Li, Wenbin; Li, Shuai; Li, Hui; Cheng, Peng; Meng, Sheng; Chen, Lan; Wu, Kehui

    2016-06-01

    A variety of two-dimensional materials have been reported in recent years, yet single-element systems such as graphene and black phosphorus have remained rare. Boron analogues have been predicted, as boron atoms possess a short covalent radius and the flexibility to adopt sp(2) hybridization, features that favour the formation of two-dimensional allotropes, and one example of such a borophene material has been reported recently. Here, we present a parallel experimental work showing that two-dimensional boron sheets can be grown epitaxially on a Ag(111) substrate. Two types of boron sheet, a β12 sheet and a χ3 sheet, both exhibiting a triangular lattice but with different arrangements of periodic holes, are observed by scanning tunnelling microscopy. Density functional theory simulations agree well with experiments, and indicate that both sheets are planar without obvious vertical undulations. The boron sheets are quite inert to oxidization and interact only weakly with their substrate. We envisage that such boron sheets may find applications in electronic devices in the future.

  20. Experimental realization of two-dimensional boron sheets

    NASA Astrophysics Data System (ADS)

    Feng, Baojie; Zhang, Jin; Zhong, Qing; Li, Wenbin; Li, Shuai; Li, Hui; Cheng, Peng; Meng, Sheng; Chen, Lan; Wu, Kehui

    2016-06-01

    A variety of two-dimensional materials have been reported in recent years, yet single-element systems such as graphene and black phosphorus have remained rare. Boron analogues have been predicted, as boron atoms possess a short covalent radius and the flexibility to adopt sp2 hybridization, features that favour the formation of two-dimensional allotropes, and one example of such a borophene material has been reported recently. Here, we present a parallel experimental work showing that two-dimensional boron sheets can be grown epitaxially on a Ag(111) substrate. Two types of boron sheet, a β12 sheet and a χ3 sheet, both exhibiting a triangular lattice but with different arrangements of periodic holes, are observed by scanning tunnelling microscopy. Density functional theory simulations agree well with experiments, and indicate that both sheets are planar without obvious vertical undulations. The boron sheets are quite inert to oxidization and interact only weakly with their substrate. We envisage that such boron sheets may find applications in electronic devices in the future.

  1. Controllable curvature from planar polymer sheets in response to light.

    PubMed

    Hubbard, Amber M; Mailen, Russell W; Zikry, Mohammed A; Dickey, Michael D; Genzer, Jan

    2017-02-24

    The ability to change shape and control curvature in 3D structures starting from planar sheets can aid in assembly and add functionality to an object. Herein, we convert planar sheets of shape memory polymers (SMPs) into 3D objects with controllable curvature by dictating where the sheets shrink. Ink patterned on the surface of the sheet absorbs infrared (IR) light, resulting in localized heating, and the material shrinks locally wherever the temperature exceeds the activation temperature, Ta. We introduce two different mechanisms for controlling curvature within SMP sheets. The 'direct' mechanism uses localized shrinkage to induce curvature only in regions patterned with ink. The 'indirect' mechanism uses localized shrinkage in regions patterned with ink to induce curvature in neighboring regions without ink through a balance of internal stresses. Finite element analysis predicts the final shape of the polymer sheets with excellent qualitative agreement with experimental studies. Results from this study show that curvature can be controlled by the distribution and darkness of the ink pattern on the polymer sheet. Additionally, we utilize the direct and indirect curvature mechanisms to demonstrate the formation and actuation of gripper devices, which represent the potential utility of this approach.

  2. Eruptive Current Sheets Trailing SOHO/LASCO CMEs

    NASA Astrophysics Data System (ADS)

    Webb, David F.

    2015-04-01

    Current sheets are important signatures of magnetic reconnection during the eruption of solar magnetic structures. Many models of eruptive flare/Coronal Mass Ejections (CMEs) involve formation of a current sheet connecting the ejecting CME flux rope with the post-eruption magnetic loop arcade. Current sheets have been interpreted in white light images as narrow rays trailing the outward-moving CME, in ultraviolet spectra as narrow, bright hot features, and with different manifestations in other wavebands. This study continues that of Webb et al. (2003), who analyzed SMM white light CMEs having candidate magnetic disconnection features at the base of the CME. About half of those were followed by coaxial, bright rays suggestive of newly formed current sheets, and Webb et al. (2003) presented detailed results of analysis of those structures. In this work we extend the study of white light eruptive current sheets to the more sensitive and extensive SOHO/LASCO coronagraph data on CMEs. We comprehensively examined all LASCO CMEs during two periods that we identify with the minimum and maximum activity of solar cycle 23. We identified ~130 ray/current sheets during these periods, nearly all of which trailed CMEs with concave-outward backs. The occurrence rate of the ray/current sheets is 6-7% of all CMEs, irrespective of the solar cycle. We analyze the rays for durations, speeds, alignments, and motions and compare the observational results with some model predictions.

  3. Effect of chloroquine and leupeptin on intracellular accumulation of amyloid-beta (A beta) 1-42 peptide in a murine N9 microglial cell line.

    PubMed

    Chu, T; Tran, T; Yang, F; Beech, W; Cole, G M; Frautschy, S A

    1998-10-09

    Murine N9 microglia accumulated A beta from media containing 0.67 microM A beta within 6 h. In N9 and in primary rat microglia, chloroquine, which disrupts lysosomal pH, increased A beta-induced accumulation of A beta, particularly A beta1-42. Leupeptin similarly enhanced A beta accumulation. The scavenger receptor antagonist fucoidan did not affect acute chloroquine-dependent A beta1-42 accumulation, demonstrating uptake of non-aggregated A beta. After prolonged incubations, chloroquine enhanced A beta multimer (8-12 kDa) accumulation, an effect inhibited by fucoidan. Disruptions of the lysosomal system enhance A beta and its multimer formation. Despite negligible effects of fucoidan on initial A beta uptake, chronic exposure inhibits multimer accumulation, demonstrating a role for scavenger receptor in multimer accumulation.

  4. Ferulic acid destabilizes preformed {beta}-amyloid fibrils in vitro

    SciTech Connect

    Ono, Kenjiro; Hirohata, Mie; Yamada, Masahito . E-mail: m-yamada@med.kanazawa-u.ac.jp

    2005-10-21

    Inhibition of the formation of {beta}-amyloid fibrils (fA{beta}), as well as the destabilization of preformed fA{beta} in the CNS, would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). We reported previously that curcumin (Cur) inhibits fA{beta} formation from A{beta} and destabilizes preformed fA{beta} in vitro. Using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies, we examined the effects of ferulic acid (FA) on the formation, extension, and destabilization of fA{beta} at pH 7.5 at 37 deg C in vitro. We next compared the anti-amyloidogenic activities of FA with Cur, rifampicin, and tetracycline. Ferulic acid dose-dependently inhibited fA{beta} formation from amyloid {beta}-peptide, as well as their extension. Moreover, it destabilized preformed fA{beta}s. The overall activity of the molecules examined was in the order of: Cur > FA > rifampicin = tetracycline. FA could be a key molecule for the development of therapeutics for AD.

  5. Perchlorate Regulatory Determination Fact Sheets

    EPA Pesticide Factsheets

    Fact sheets have been developed for the perchlorate regulatory determination corresponding to the following stages published in the Federal Register: Final, Supplemental request for comments, and Preliminary.

  6. Ice sheets and nitrogen

    PubMed Central

    Wolff, Eric W.

    2013-01-01

    Snow and ice play their most important role in the nitrogen cycle as a barrier to land–atmosphere and ocean–atmosphere exchanges that would otherwise occur. The inventory of nitrogen compounds in the polar ice sheets is approximately 260 Tg N, dominated by nitrate in the much larger Antarctic ice sheet. Ice cores help to inform us about the natural variability of the nitrogen cycle at global and regional scale, and about the extent of disturbance in recent decades. Nitrous oxide concentrations have risen about 20 per cent in the last 200 years and are now almost certainly higher than at any time in the last 800 000 years. Nitrate concentrations recorded in Greenland ice rose by a factor of 2–3, particularly between the 1950s and 1980s, reflecting a major change in NOx emissions reaching the background atmosphere. Increases in ice cores drilled at lower latitudes can be used to validate or constrain regional emission inventories. Background ammonium concentrations in Greenland ice show no significant recent trend, although the record is very noisy, being dominated by spikes of input from biomass burning events. Neither nitrate nor ammonium shows significant recent trends in Antarctica, although their natural variations are of biogeochemical and atmospheric chemical interest. Finally, it has been found that photolysis of nitrate in the snowpack leads to significant re-emissions of NOx that can strongly impact the regional atmosphere in snow-covered areas. PMID:23713125

  7. Ice sheets and nitrogen.

    PubMed

    Wolff, Eric W

    2013-07-05

    Snow and ice play their most important role in the nitrogen cycle as a barrier to land-atmosphere and ocean-atmosphere exchanges that would otherwise occur. The inventory of nitrogen compounds in the polar ice sheets is approximately 260 Tg N, dominated by nitrate in the much larger Antarctic ice sheet. Ice cores help to inform us about the natural variability of the nitrogen cycle at global and regional scale, and about the extent of disturbance in recent decades. Nitrous oxide concentrations have risen about 20 per cent in the last 200 years and are now almost certainly higher than at any time in the last 800 000 years. Nitrate concentrations recorded in Greenland ice rose by a factor of 2-3, particularly between the 1950s and 1980s, reflecting a major change in NOx emissions reaching the background atmosphere. Increases in ice cores drilled at lower latitudes can be used to validate or constrain regional emission inventories. Background ammonium concentrations in Greenland ice show no significant recent trend, although the record is very noisy, being dominated by spikes of input from biomass burning events. Neither nitrate nor ammonium shows significant recent trends in Antarctica, although their natural variations are of biogeochemical and atmospheric chemical interest. Finally, it has been found that photolysis of nitrate in the snowpack leads to significant re-emissions of NOx that can strongly impact the regional atmosphere in snow-covered areas.

  8. Dynamics of charged current sheets at high-latitude magnetopause

    NASA Astrophysics Data System (ADS)

    Savin, S.; Amata, E.; Zelenyi, L.; Dunlop, M.; Andre, M.; Song, P.; Blecki, J.; Buechner, J.; Rauch, J. L.; Skalsky, A.

    E. Amata (2), L. Zelenyi (1), M. Dunlop (3), M. Andre (4), P. Song (5), J. Blecki (6), J. Buechner (7), J.L Rauch, J.G. Trotignon (8), G. Consolini, F. Marcucci (2), B. Nikutowski (7), A. Skalsky, S. Romanov, E. Panov (1) (2) IFSI, Roma, Italy, (3) RAL, UK, (4) IRFU, Uppsala, Sweden, (5) U. Mass. Lowell, USA, (6) SRC, Warsaw, Poland, (7) MPAe, Germany, (8) LPCE, Orleans, France; We study dynamics of thin current sheets over polar cusps from data of Interball-1 and Cluster. At the high-beta magnetopause current sheet width often reaches ion gyroradius scales, that leads to their Hall dynamics in the presence of local surface charges. Respective perpendicular electric fields provide the means for momentum coupling through the current sheets and are able to accelerate ions with gyroradius of the order or larger than the sheet width. At borders of large diamagnetic cavities this mechanism is able to support mass exchange and accelerate/ heat incoming magnetosheath particles. At larger scales the inhomogeneous electric fields at the current sheet borders can accelerate incident plasma downtail along magnetopause via inertial drift. It serves to move external plasma away for dynamic equilibrium supporting. Farther away from magnetopause similar nonlinear electric field wave trains, selfconsistently produced by interaction of reflected from the obstacle waves with magnetosheath fluctuations, destroy the incident flux into accelerated magnetosonic jets and decelerated Alfvenic flows and generate small-scale current sheets due to different sign of electron and ion inertial drift in the nonlinear electric field bursts. We suggest that this direct kinetic energy transformation creates current sheets with anomalous statistics of field rotation angles in the turbulent boundary layer in front of magnetopause, which have been attributed earlier to an intermittent turbulence. We compare measured spectra with a model of nonlinear system with intermittent chaotic behavior. Work was

  9. Modeling the formation of secondary organic aerosol (SOA). 2. The predicted effects of relative humidity on aerosol formation in the alpha-pinene-, beta-pinene-, sabinene-, delta 3-carene-, and cyclohexene-ozone systems.

    PubMed

    Seinfeld, J H; Erdakos, G B; Asher, W E; Pankow, J F

    2001-05-01

    Atmospheric oxidation of volatile organic compounds can lead to the formation of secondary organic aerosol (SOA) through the gas/particle (G/P) partitioning of the oxidation products. Since water is ubiquitous in the atmosphere, the extent of the partitioning for any individual organic product depends not only on the amounts and properties of the partitioning organic compounds, but also on the amount of water present. Predicting the effects of water on the atmospheric G/P distributions of organic compounds is, therefore, central to understanding SOA formation. The goals of the current work are to gain understanding of how increases in RH affect (1) overall SOA yields, (2) water uptake by SOA, (3) the behaviors of individual oxidation products, and (4) the fundamental physical properties of the SOA phase that govern the G/P distribution of each of the oxidation products. Part 1 of this series considered SOA formation from five parent hydrocarbons in the absence of water. This paper predicts how adding RH to those systems uniformly increases both the amount of condensed organic mass and the amount of liquid water in the SOA phase. The presence of inorganic components is not considered. The effect of increasing RH is predicted to be stronger for SOA produced from cyclohexene as compared to SOA produced from four monoterpenes. This is likely a result of the greater general degree of oxidation (and hydrophilicity) of the cyclohexene products. Good agreement was obtained between predicted SOA yields and laboratory SOA yield data actually obtained in the presence of water. As RH increases, the compounds that play the largest roles in changing both the organic and water masses in the SOA phase are those with vapor pressures that are intermediate between those of essentially nonvolatile and highly volatile species. RH-driven changes in the compound-dependent G/P partitioning coefficient Kp result from changes in both the average molecular weight MWom of the absorbing

  10. Structural and Functional Properties of Peptides Based on the N-terminus of HIV-1 gp41 and the C-terminus of the Amyloid-Beta Protein

    PubMed Central

    Gordon, Larry M.; Nisthal, Alex; Lee, Andy B.; Eskandari, Sepehr; Ruchala, Piotr; Jung, Chun-Ling; Waring, Alan J.; Mobley, Patrick W.

    2008-01-01

    Given their high alanine and glycine levels, plaque formation, α-helix to β-sheet interconversion and fusogenicity, FP (i.e., the N-terminal fusion peptide of HIV-1 gp41; 23 residues) and amyloids were proposed as belonging to the same protein superfamily. Here, we further test whether FP may exhibit ‘amyloid-like’ characteristics, by contrasting its structural and functional properties with those of Aβ(26–42), a 17-residue peptide from the C-terminus of the amyloid-beta protein responsible for Alzheimer’s. FTIR spectroscopy, electron microscopy, light scattering and predicted amyloid structure aggregation (PASTA) indicated that aqueous FP and Aβ(26–42) formed similar networked β-sheet fibrils, although the FP fibril interactions were weaker. FP and Aβ(26–42) both lysed and aggregated human erythrocytes, with the hemolysis-onsets correlated with the conversion of α-helix to β-sheet for each peptide in liposomes. Congo red (CR), a marker of amyloid plaques in situ, similarly inhibited either FP- or Aβ(26–42)-induced hemolysis, and surface plasmon resonance indicated that this may be due to direct CR-peptide binding. These findings suggest that membrane-bound β-sheets of FP may contribute to the cytopathicity of HIV in vivo through an amyloid-type mechanism, and support the classification of HIV-1 FP as an ‘amyloid homolog’ (or ‘amylog’). PMID:18515070

  11. Laminated sheet composites reinforced with modular filament sheet

    NASA Technical Reports Server (NTRS)

    Reece, O. Y.

    1968-01-01

    Aluminum and magnesium composite sheet laminates reinforced with low density, high strength modular filament sheets are produced by diffusion bonding and explosive bonding. Both processes are accomplished in normal atmosphere and require no special tooling or cleaning other than wire brushing the metal surfaces just prior to laminating.

  12. 17. INTAKE PIER, BRIDGE STRESS SHEET, SHEET 8 OF 117, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. INTAKE PIER, BRIDGE STRESS SHEET, SHEET 8 OF 117, 1920. - Sacramento River Water Treatment Plant Intake Pier & Access Bridge, Spanning Sacramento River approximately 175 feet west of eastern levee on river; roughly .5 mile downstream from confluence of Sacramento & American Rivers, Sacramento, Sacramento County, CA

  13. ISEE observations of the plasma sheet boundary, plasma sheet, and neutral sheet. I - Electric field, magnetic field, plasma, and ion composition

    NASA Technical Reports Server (NTRS)

    Cattell, C. A.; Mozer, F. S.; Hones, E. W., Jr.; Anderson, R. R.; Sharp, R. D.

    1986-01-01

    The first simultaneous study of dc and ac electric and magnetic fields, E x B velocity, plasma flows, ratio of plasma to magnetic field pressure, total energy density, energetic particles, and ion composition from the ISEE satellites and ground and interplanetary magnetic fields has been made to determine (1) the relationship of the previously observed electric fields at the plasma sheet boundary and at the neutral sheet to plasma parameters, and (2) whether the phenomena occurring during quiet and active times were consistent with the formation of a near-earth neutral line during substorms or with the boundary layer model. Five observations made during the study of two substorms were seen to be in agreement with the neutral-line model. The observations are consistent with the satellite being located at varying distances from the neutral line and diffusion region where reconnection and plasma acceleration were occurring. Although the z component (into or out of the ecliptic plane) of E x B convection was generally toward the neutral sheet, there were examples when it was consistent with the inferred motion of the plasma sheet past the satellite. A synthesis of previous reports on large electric fields at the plasma sheet boundary and variable fields at the neutral sheet including the associated plasma flows is also described.

  14. beta-Hexachlorocyclohexane (beta-HCH)

    Integrated Risk Information System (IRIS)

    beta - Hexachlorocyclohexane ( beta - HCH ) ; CASRN 319 - 85 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Asses

  15. Core binding factor beta (Cbfβ) controls the balance of chondrocyte proliferation and differentiation by upregulating Indian hedgehog (Ihh) expression and inhibiting parathyroid hormone-related protein receptor (PPR) expression in postnatal cartilage and bone formation.

    PubMed

    Tian, Fei; Wu, Mengrui; Deng, Lianfu; Zhu, Guochun; Ma, Junqing; Gao, Bo; Wang, Lin; Li, Yi-Ping; Chen, Wei

    2014-07-01

    Core binding factor beta (Cbfβ) is essential for embryonic bone morphogenesis. Yet the mechanisms by which Cbfβ regulates chondrocyte proliferation and differentiation as well as postnatal cartilage and bone formation remain unclear. Hence, using paired-related homeobox transcription factor 1-Cre (Prx1-Cre) mice, mesenchymal stem cell-specific Cbfβ-deficient (Cbfβ(f/f) Prx1-Cre) mice were generated to study the role of Cbfβ in postnatal cartilage and bone development. These mutant mice survived to adulthood but exhibited severe sternum and limb malformations. Sternum ossification was largely delayed in the Cbfβ(f/f) Prx1-Cre mice and the xiphoid process was noncalcified and enlarged. In newborn and 7-day-old Cbfβ(f/f) Prx1-Cre mice, the resting zone was dramatically elongated, the proliferation zone and hypertrophic zone of the growth plates were drastically shortened and disorganized, and trabecular bone formation was reduced. Moreover, in 1-month-old Cbfβ(f/f) Prx1-Cre mice, the growth plates were severely deformed and trabecular bone was almost absent. In addition, Cbfβ deficiency impaired intramembranous bone formation both in vivo and in vitro. Interestingly, although the expression of Indian hedgehog (Ihh) was largely reduced, the expression of parathyroid hormone-related protein (PTHrP) receptor (PPR) was dramatically increased in the Cbfβ(f/f) Prx1-Cre growth plate, indicating that that Cbfβ deficiency disrupted the Ihh-PTHrP negative regulatory loop. Chromatin immunoprecipitation (ChIP) analysis and promoter luciferase assay demonstrated that the Runx/Cbfβ complex binds putative Runx-binding sites of the Ihh promoter regions, and also the Runx/Cbfβ complex directly upregulates Ihh expression at the transcriptional level. Consistently, the expressions of Ihh target genes, including CyclinD1, Ptc, and Pthlh, were downregulated in Cbfβ-deficient chondrocytes. Taken together, our study reveals not only that Cbfβ is essential for chondrocyte

  16. Method for heating a glass sheet

    DOEpatents

    Boaz, P.T.

    1998-07-21

    A method for heating a glass sheet includes the steps of heating a glass sheet to a first predetermined temperature and applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature to allow the glass sheet to be formed. 5 figs.

  17. Method for heating a glass sheet

    DOEpatents

    Boaz, Premakaran Tucker

    1998-01-01

    A method for heating a glass sheet includes the steps of heating a glass sheet to a first predetermined temperature and applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature to allow the glass sheet to be formed.

  18. An amino acid code for β-sheet packing structure.

    PubMed

    Joo, Hyun; Tsai, Jerry

    2014-09-01

    To understand the relationship between protein sequence and structure, this work extends the knob-socket model in an investigation of β-sheet packing. Over a comprehensive set of β-sheet folds, the contacts between residues were used to identify packing cliques: sets of residues that all contact each other. These packing cliques were then classified based on size and contact order. From this analysis, the two types of four-residue packing cliques necessary to describe β-sheet packing were characterized. Both occur between two adjacent hydrogen bonded β-strands. First, defining the secondary structure packing within β-sheets, the combined socket or XY:HG pocket consists of four residues i, i+2 on one strand and j, j+2 on the other. Second, characterizing the tertiary packing between β-sheets, the knob-socket XY:H+B consists of a three-residue XY:H socket (i, i+2 on one strand and j on the other) packed against a knob B residue (residue k distant in sequence). Depending on the packing depth of the knob B residue, two types of knob-sockets are found: side-chain and main-chain sockets. The amino acid composition of the pockets and knob-sockets reveal the sequence specificity of β-sheet packing. For β-sheet formation, the XY:HG pocket clearly shows sequence specificity of amino acids. For tertiary packing, the XY:H+B side-chain and main-chain sockets exhibit distinct amino acid preferences at each position. These relationships define an amino acid code for β-sheet structure and provide an intuitive topological mapping of β-sheet packing.

  19. Tryptophan fluorescence monitors structural changes accompanying signalling state formation in the photocycle of photoactive yellow protein.

    PubMed

    Gensch, Thomas; Hendriks, Johnny; Hellingwerf, Klaas J

    2004-06-01

    Photoactive yellow protein, a small, water-soluble blue-light absorbing photoreceptor protein from Ectothiorhodospira(Halorhodospira)[space]halophila has a structure with two hydrophobic cores, of which the main one houses its light-sensitive chromophore (p-coumaric acid), separated by a central [small beta]-sheet. This photoreceptor protein contains a single tryptophan residue (W119) that is situated at the interface between the central beta-sheet and its N-terminal cap. The fluorescence properties of W119 in the dark state pG (lambda(max)= 328 nm; Phi(fl)= 0.01; nearly pH-independent) are typical for a buried tryptophan in a hydrophobic environment with significant quenching by nearby amino acid residues. Signalling state formation leads to pH-dependent fluorescence changes: At pH values <6.5 the fluorescence emission increases, with a minor blue shift of the emission maximum. Above this pH, the emission maximum of the tryptophan shifts considerably to the red, whereas its total intensity decreases. These results further support the contention that signalling state formation in PYP leads to significant changes in the structure of this protein, even at sites that are at a considerable distance from the chromophore. The nature of these changes in pB, however, depend upon the pH imposed upon the protein: At slightly alkaline pH, which presumably is closest to the pH to which this protein is exposed in vivo, these changes lead to an exposure of the part of the central beta-sheet harbouring W119. At slightly acidic pH the polarity of the environment of W119 is hardly affected by the formation of the signalling state but the quenching of its fluorescence emission, possibly by nearby amino acids, is reduced. On the other hand, its accessibility for quenching by small molecules in the solution is enhanced at acidic and alkaline pH in the signalling state (pB) compared to the dark state (pG). This latter observation points towards a more flexible structure of the N

  20. Photovoltaics Fact Sheet

    SciTech Connect

    2016-02-01

    This fact sheet is an overview of the Photovoltaics (PV) subprogram at the U.S. Department of Energy SunShot Initiative. The U.S. Department of Energy (DOE)’s Solar Energy Technologies Office works with industry, academia, national laboratories, and other government agencies to advance solar PV, which is the direct conversion of sunlight into electricity by a semiconductor, in support of the goals of the SunShot Initiative. SunShot supports research and development to aggressively advance PV technology by improving efficiency and reliability and lowering manufacturing costs. SunShot’s PV portfolio spans work from early-stage solar cell research through technology commercialization, including work on materials, processes, and device structure and characterization techniques.

  1. Systems Integration Fact Sheet

    SciTech Connect

    2016-06-01

    This fact sheet is an overview of the Systems Integration subprogram at the U.S. Department of Energy SunShot Initiative. The Systems Integration subprogram enables the widespread deployment of safe, reliable, and cost-effective solar energy technologies by addressing the associated technical and non-technical challenges. These include timely and cost-effective interconnection procedures, optimal system planning, accurate prediction of solar resources, monitoring and control of solar power, maintaining grid reliability and stability, and many more. To address the challenges associated with interconnecting and integrating hundreds of gigawatts of solar power onto the electricity grid, the Systems Integration program funds research, development, and demonstration projects in four broad, interrelated focus areas: grid performance and reliability, dispatchability, power electronics, and communications.

  2. Hyperspectral light sheet microscopy

    NASA Astrophysics Data System (ADS)

    Jahr, Wiebke; Schmid, Benjamin; Schmied, Christopher; Fahrbach, Florian O.; Huisken, Jan

    2015-09-01

    To study the development and interactions of cells and tissues, multiple fluorescent markers need to be imaged efficiently in a single living organism. Instead of acquiring individual colours sequentially with filters, we created a platform based on line-scanning light sheet microscopy to record the entire spectrum for each pixel in a three-dimensional volume. We evaluated data sets with varying spectral sampling and determined the optimal channel width to be around 5 nm. With the help of these data sets, we show that our setup outperforms filter-based approaches with regard to image quality and discrimination of fluorophores. By spectral unmixing we resolved overlapping fluorophores with up to nanometre resolution and removed autofluorescence in zebrafish and fruit fly embryos.

  3. Soft Costs Fact Sheet

    SciTech Connect

    2016-05-01

    This fact sheet is an overview of the systems integration subprogram at the U.S. Department of Energy SunShot Initiative. Soft costs can vary significantly as a result of a fragmented energy marketplace. In the U.S., there are 18,000 jurisdictions and 3,000 utilities with different rules and regulations for how to go solar. The same solar equipment may vary widely in its final installation price due to process and market variations across jurisdictions, creating barriers to rapid industry growth. SunShot supports the development of innovative solutions that enable communities to build their local economies and establish clean energy initiatives that meet their needs, while at the same time creating sustainable solar market conditions.

  4. Cutting Guide for Fibrous Sheets

    NASA Technical Reports Server (NTRS)

    Warren, A., D.

    1985-01-01

    Tool facilitates repetitive cutting of fibrous sheets. Flexible aluminum tape allows metal strips folded back on themselves, exposing fresh material for cutting. More than one strip folded back, and cutting width therefore increased in multiples of strip width. Developed for cutting strips of alumina-fiber matting, tool also used on such materials as felts, textiles, and sheet metals.

  5. Silicone Coating on Polyimide Sheet

    NASA Technical Reports Server (NTRS)

    Park, J. J.

    1985-01-01

    Silicone coatings applied to polyimide sheeting for variety of space-related applications. Coatings intended to protect flexible substrates of solar-cell blankets from degradation by oxygen atoms, electrons, plasmas, and ultraviolet light in low Earth orbit and outer space. Since coatings are flexible, generally useful in forming flexible laminates or protective layers on polyimide-sheet products.

  6. Communication Fact Sheets for Parents.

    ERIC Educational Resources Information Center

    Stremel, Kathleen; Bixler, Betsy; Morgan, Susanne; Layton, Kristen

    This booklet contains 28 fact sheets on communication written primarily for parents and families with a child who is deaf-blind. They attempt to address fundamental but complex issues related to the communication needs of children with vision and hearing impairments. Each fact sheet targets a specific area, including: (1) communication; (2)…

  7. Ganges Chasma Sand Sheet

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

    Today's sand sheet is located in the Ganges Chasma portion of Valles Marineris. As with yesterday's image, note that the dune forms are seen only at the margin and that the interior of the sand sheet at this resolution appears to completely lack dune forms.

    Image information: VIS instrument. Latitude -6.4, Longitude 310.7 East (49.3 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  8. Vertically scanned laser sheet microscopy.

    PubMed

    Dong, Di; Arranz, Alicia; Zhu, Shouping; Yang, Yujie; Shi, Liangliang; Wang, Jun; Shen, Chen; Tian, Jie; Ripoll, Jorge

    2014-01-01

    Laser sheet microscopy is a widely used imaging technique for imaging the three-dimensional distribution of a fluorescence signal in fixed tissue or small organisms. In laser sheet microscopy, the stripe artifacts caused by high absorption or high scattering structures are very common, greatly affecting image quality. To solve this problem, we report here a two-step procedure which consists of continuously acquiring laser sheet images while vertically displacing the sample, and then using the variational stationary noise remover (VSNR) method to further reduce the remaining stripes. Images from a cleared murine colon acquired with a vertical scan are compared with common stitching procedures demonstrating that vertically scanned light sheet microscopy greatly improves the performance of current light sheet microscopy approaches without the need for complex changes to the imaging setup and allows imaging of elongated samples, extending the field of view in the vertical direction.

  9. Plasma Relaxation Dynamics Moderated by Current Sheets

    NASA Astrophysics Data System (ADS)

    Dewar, Robert; Bhattacharjee, Amitava; Yoshida, Zensho

    2014-10-01

    Ideal magnetohydrodynamics (IMHD) is strongly constrained by an infinite number of microscopic constraints expressing mass, entropy and magnetic flux conservation in each infinitesimal fluid element, the latter preventing magnetic reconnection. By contrast, in the Taylor-relaxed equilibrium model all these constraints are relaxed save for global magnetic flux and helicity. A Lagrangian is presented that leads to a new variational formulation of magnetized fluid dynamics, relaxed MHD (RxMHD), all static solutions of which are Taylor equilibrium states. By postulating that some long-lived macroscopic current sheets can act as barriers to relaxation, separating the plasma into multiple relaxation regions, a further generalization, multi-relaxed MHD (MRxMHD), is developed. These concepts are illustrated using a simple two-region slab model similar to that proposed by Hahm and Kulsrud--the formation of an initial shielding current sheet after perturbation by boundary rippling is calculated using MRxMHD and the final island state, after the current sheet has relaxed through a reconnection sequence, is calculated using RxMHD. Australian Research Council Grant DP110102881.

  10. Active volcanism beneath the West Antarctic ice sheet and implications for ice-sheet stability

    USGS Publications Warehouse

    Blankenship, D.D.; Bell, R.E.; Hodge, S.M.; Brozena, J.M.; Behrendt, John C.; Finn, C.A.

    1993-01-01

    IT is widely understood that the collapse of the West Antarctic ice sheet (WAIS) would cause a global sea level rise of 6 m, yet there continues to be considerable debate about the detailed response of this ice sheet to climate change1-3. Because its bed is grounded well below sea level, the stability of the WAIS may depend on geologically controlled conditions at the base which are independent of climate. In particular, heat supplied to the base of the ice sheet could increase basal melting and thereby trigger ice streaming, by providing the water for a lubricating basal layer of till on which ice streams are thought to slide4,5. Ice streams act to protect the reservoir of slowly moving inland ice from exposure to oceanic degradation, thus enhancing ice-sheet stability. Here we present aerogeophysical evidence for active volcanism and associated elevated heat flow beneath the WAIS near the critical region where ice streaming begins. If this heat flow is indeed controlling ice-stream formation, then penetration of ocean waters inland of the thin hot crust of the active portion of the West Antarctic rift system could lead to the disappearance of ice streams, and possibly trigger a collapse of the inland ice reservoir.

  11. The Rapid Ice Sheet Change Observatory (RISCO)

    NASA Astrophysics Data System (ADS)

    Morin, P.; Howat, I. M.; Ahn, Y.; Porter, C.; McFadden, E. M.

    2010-12-01

    The recent expansion of observational capacity from space has revealed dramatic, rapid changes in the Earth’s ice cover. These discoveries have fundamentally altered how scientists view ice-sheet change. Instead of just slow changes in snow accumulation and melting over centuries or millennia, important changes can occur in sudden events lasting only months, weeks, or even a single day. Our understanding of these short time- and space-scale processes, which hold important implications for future global sea level rise, has been impeded by the low temporal and spatial resolution, delayed sensor tasking, incomplete coverage, inaccessibility and/or high cost of data available to investigators. New cross-agency partnerships and data access policies provide the opportunity to dramatically improve the resolution of ice sheet observations by an order of magnitude, from timescales of months and distances of 10’s of meters, to days and meters or less. Advances in image processing technology also enable application of currently under-utilized datasets. The infrastructure for systematically gathering, processing, analyzing and distributing these data does not currently exist. Here we present the development of a multi-institutional, multi-platform observatory for rapid ice change with the ultimate objective of helping to elucidate the relevant timescales and processes of ice sheet dynamics and response to climate change. The Rapid Ice Sheet Observatory (RISCO) gathers observations of short time- and space-scale Cryosphere events and makes them easily accessible to investigators, media and general public. As opposed to existing data centers, which are structured to archive and distribute diverse types of raw data to end users with the specialized software and skills to analyze them, RISCO focuses on three types of geo-referenced raster (image) data products in a format immediately viewable with commonly available software. These three products are (1) sequences of images

  12. Quantitative analysis of simvastatin and its beta-hydroxy acid in human plasma using automated liquid-liquid extraction based on 96-well plate format and liquid chromatography-tandem mass spectrometry.

    PubMed

    Zhang, Nanyan; Yang, Amy; Rogers, John Douglas; Zhao, Jamie J

    2004-01-27

    An assay based on automated liquid-liquid extraction (LLE) and liquid chromatography-tandem mass spectrometry (LC/MS/MS) has been developed and validated for the quantitative analysis of simvastatin (SV) and its beta-hydroxy acid (SVA) in human plasma. A Packard MultiProbe II workstation was used to convert human plasma samples collected following administration of simvastatin and quality control (QC) samples from individual tubes into 96-well plate format. The workstation was also used to prepare calibration standards and spike internal standards. A Tomtec Quadra 96-channel liquid handling workstation was used to perform LLE based on 96-well plates including adding solvents, separating organic from aqueous layer and reconstitution. SV and SVA were separated through a Kromasil C18 column (50 mm x 2 mm i.d., 5 microm) and detected by tandem mass spectrometry with a TurboIonspray interface. Stable isotope-labeled SV and SVA, 13CD(3)-SV and 13 CD(3)-SVA, were used as the internal standards for SV and SVA, respectively. The automated procedures reduced the overall analytical time (96 samples) to 1/3 of that of manual LLE. Most importantly, an analyst spent only a fraction of time on the 96-well LLE. A limit of quantitation of 50 pg/ml was achieved for both SV and SVA. The interconversion between SV and SVA during the 96-well LLE was found to be negligible. The assay showed very good reproducibility, with intra- and inter-assay precision (%R.S.D.) of less than 7.5%, and accuracy of 98.7-102.3% of nominal values for both analytes. By using this method, sample throughput should be enhanced at least three-fold compared to that of the manual procedure.

  13. A Single Mutation at the Sheet Switch Region Results in Conformational Changes Favoring 6 Light-Chain Fibrillogenesis

    SciTech Connect

    Hernández-Santoyo, A.; Del Pozo Yauner, L; Fuentes-Silva, D; Ortiz, E; Rudiño-Piñera, E; Sánchez-López, R; Horjales, E; Becerril, B; Rodríguez-Romero, A

    2010-01-01

    Systemic amyloid light-chain (LC) amyloidosis is a disease process characterized by the pathological deposition of monoclonal LCs in tissue. All LC subtypes are capable of fibril formation although {lambda} chains, particularly those belonging to the {lambda}6 type, are overrepresented. Here, we report the thermodynamic and in vitro fibrillogenic properties of several mutants of the {lambda}6 protein 6aJL2 in which Pro7 and/or His8 was substituted by Ser or Pro. The H8P and H8S mutants were almost as stable as the wild-type protein and were poorly fibrillogenic. In contrast, the P7S mutation decreased the thermodynamic stability of 6aJL2 and greatly enhanced its capacity to form amyloid-like fibrils in vitro. The crystal structure of the P7S mutant showed that the substitution induced both local and long-distance effects, such as the rearrangement of the VL (variable region of the light chain)-VL interface. This mutant crystallized in two orthorhombic polymorphs, P2{sub 1}2{sub 1}2{sub 1} and C222{sub 1}. In the latter, a monomer that was not arranged in the typical Bence-Jones dimer was observed for the first time. Crystal-packing analysis of the C222{sub 1} lattice showed the establishment of intermolecular {beta}-{beta} interactions that involved the N-terminus and {beta}-strand B and that these could be relevant in the mechanism of LC fibril formation. Our results strongly suggest that Pro7 is a key residue in the conformation of the N-terminal sheet switch motif and, through long-distance interactions, is also critically involved in the contacts that stabilized the VL interface in {lambda}6 LCs.

  14. Penguin Fact Sheet.

    ERIC Educational Resources Information Center

    Flotsam and Jetsam: A Newsletter for Massachusetts Marine Educators, 1985

    1985-01-01

    Presents factual information on penguins using an outline format. Includes descriptions of physical characteristics, behavioral mechanisms, geographical distribution, and physiological processes. Provides separate bibliographies for teachers and students. (ML)

  15. [Clip Sheets from BOCES. Opportunities. Health. Careers. = Oportunidades. Salud. Una Camera En...

    ERIC Educational Resources Information Center

    State Univ. of New York, Geneseo. Coll. at Geneseo. Migrant Center.

    This collection of 83 clip sheets, or classroom handouts, was created to help U.S. migrants learn more about health, careers, and general "opportunities" including education programs. They are written in both English and Spanish and are presented in an easily understandable format. Health clip-sheet topics include the following: Abuse; AIDS;…

  16. Current sheet thinning, reconnection onset, and auroral morphology during geomagnetic substorms

    NASA Astrophysics Data System (ADS)

    Otto, A.; Hsieh, M. S.

    2015-12-01

    Geomagnetic substorms represent a fundamental energy release mechanism for the terrestrial magnetosphere. Specifically, the evolution of thin currents sheets during the substorm growth phase plays a key role for substorms because such current sheets present a much lower threshold for the onset of tearing modes and magnetic reconnection than the usually thick magnetotail current sheet. Here we examine and compare two basic processes for current sheet thinning in the Earth's magnetotail: Current sheet thinning (1) through closed magnetic flux depletion (MFD) in the near Earth magnetotail caused by divergent flux transport to replace closed flux on the dayside and (2) through accumulation of open flux magnetic flux in the tail lobes also caused by dayside reconnection. Both processes are expected to operate during any period of enhanced dayside reconnection. It is demonstrated that closed magnetic flux depletion (MFD) in the near Earth magnetotail and the increase of open lobe magnetic flux can lead to the evolution of two separate thin current sheets in the near Earth and the mid tail regions of the magnetosphere. While the auroral morphology associated with MFD and near Earth current sheet formation is well consistent with typical substorm growth observation, midtail current sheet formation through lobe flux increase shows only a minor influence on the auroral ionosphere. We discuss the physics of the dual current sheet formation and local and auroral properties of magnetic reconnection in either current sheet. It is suggested that only reconnection onset in the near Earth current sheet may be consistent with substorm expansion because the flux tube entropy depletion of mid tail reconnection appears insufficient to cause geosynchronous particle injection and dipolarization. Therefore reconnection in the mid tail current sheet is more likely associated with bursty bulk flows or dipolarization fronts which stop short of geosynchronous distances.

  17. The quantitative inspection of iron aluminide green sheet using transient thermography

    NASA Astrophysics Data System (ADS)

    Watkins, Michael L.; Hinders, Mark K.; Scorey, Clive; Winfree, William

    1999-12-01

    The recent development of manufacturing techniques for the fabrication of thin iron aluminide, FeAl, sheet requires advanced quantitative methods for on-line inspection. An understanding of the mechanisms responsible for flaws and the development of appropriate flaw detection methods are key elements in an effective quality management system. The first step in the fabrication of thin FeAl alloy sheet is the formation of a green sheet, either by cold rolling or tape casting FeAl powder mixed with organic binding agents. The finished sheet is obtained using a series of process steps involving binder elimination, densification, sintering, and annealing. Non-uniformities within the green sheet are the major contributor to material failure in subsequent sheet processing and the production of non-conforming finished sheet. Previous work has demonstrated the advantages of using active thermography to detect the flaws and heterogeneity within green powder composites (1)(2)(3). The production environment and physical characteristics of these composites provide for unique challenges in developing a rapid nondestructive inspection capability. Thermography is non-contact and minimizes the potential damage to the fragile green sheet. Limited access to the material also demands a one-sided inspection technique. In this paper, we will describe the application of thermography for 100% on-line inspection within an industrial process. This approach is cost competitive with alternative technologies, such as x-ray imaging systems, and provides the required sensitivity to the variations in material composition. The formation of green sheet flaws and their transformation into defects within intermediate and finished sheet products will be described. A green sheet conformance criterion will be presented which would significantly reduce the probability of processing poor quality green sheet which contributes to higher waste and inferior bulk alloy sheet.

  18. The quantitative inspection of iron aluminide green sheet using transient thermography

    SciTech Connect

    Watkins, Michael L.; Hinders, Mark K.; Scorey, Clive; Winfree, William

    1999-12-02

    The recent development of manufacturing techniques for the fabrication of thin iron aluminide, FeAl, sheet requires advanced quantitative methods for on-line inspection. An understanding of the mechanisms responsible for flaws and the development of appropriate flaw detection methods are key elements in an effective quality management system. The first step in the fabrication of thin FeAl alloy sheet is the formation of a green sheet, either by cold rolling or tape casting FeAl powder mixed with organic binding agents. The finished sheet is obtained using a series of process steps involving binder elimination, densification, sintering, and annealing. Non-uniformities within the green sheet are the major contributor to material failure in subsequent sheet processing and the production of non-conforming finished sheet. Previous work has demonstrated the advantages of using active thermography to detect the flaws and heterogeneity within green powder composites (1)(2)(3). The production environment and physical characteristics of these composites provide for unique challenges in developing a rapid nondestructive inspection capability. Thermography is non-contact and minimizes the potential damage to the fragile green sheet. Limited access to the material also demands a one-sided inspection technique. In this paper, we will describe the application of thermography for 100% on-line inspection within an industrial process. This approach is cost competitive with alternative technologies, such as x-ray imaging systems, and provides the required sensitivity to the variations in material composition. The formation of green sheet flaws and their transformation into defects within intermediate and finished sheet products will be described. A green sheet conformance criterion will be presented which would significantly reduce the probability of processing poor quality green sheet which contributes to higher waste and inferior bulk alloy sheet.

  19. Treatment of refractory cutaneous ulcers with mixed sheets consisting of peripheral blood mononuclear cells and fibroblasts

    PubMed Central

    Ueno, Koji; Takeuchi, Yuriko; Samura, Makoto; Tanaka, Yuya; Nakamura, Tamami; Nishimoto, Arata; Murata, Tomoaki; Hosoyama, Tohru; Hamano, Kimikazu

    2016-01-01

    The purpose of this study was to confirm the therapeutic effects of mixed sheets consisting of peripheral blood mononuclear cells (PBMNCs) and fibroblasts on cutaneous skin ulcers. Vascular endothelial growth factor (VEGF) secretion in mixed cell sheets was much higher than in PBMNCs and fibroblasts. Concerning the mechanism, transforming growth factor beta 1 and platelet-derived growth factor BB secreted from PBMNCs enhanced VEGF production in fibroblasts. In wounds created on the backs of diabetic mice, the therapeutic effect of mixed cell sheets was similar to that of daily treatment with trafermin, a recombinant human basic fibroblast growth factor. Although abnormal granulation tissue and inflammatory cell infiltration were observed in trafermin-treated wounds, the transplantation of mixed cell sheets resulted in the natural anatomy of subcutaneous tissues. The expression patterns of identical wound-healing factors in wounds were different between mixed sheet-transfected and trafermin-treated animals. Because mixed cell sheets transplanted into full-thickness skin defects were eliminated in hosts by day 21 in syngeneic transplantation models, allogeneic transplantation was performed using mice with different genetic backgrounds. The wound-healing rates were similar between the mixed cell sheet and trafermin groups. Our data indicated that mixed cell sheets represent a promising therapeutic material for cutaneous ulcers. PMID:27329845

  20. Polymerization of Diacetylene Using β-SHEET as a Template

    NASA Astrophysics Data System (ADS)

    Mori, Takeshi; Fukawa, Yoichi; Shimoyama, Kenji; Minagawa, Keiji; Tanaka, Masami

    In the parallel and anti-parallel β-sheet structures, hydrogen bonding arises between the amide bonds of the peptide chains to arrange them with a distance of ca. 5 Å. That distance matched with the repeating unit distance of polydiacetylene. In this study, the effectiveness of the β-sheet as a template for the polymerization of diacetylene was examined by using diacetylene-introduced oligopeptides. The diacetylene-introduced amino acid (Thr(DA)) was synthesized from L-threonine. Though peptides Ac-Thr(DA)-NHMe and Ac-[Thr(DA)]2-NHMe formed anti-parallel β-sheet, they showed slight or no polymerization in both of the solid and the solution states. On the other hand, Ac-[Thr(DA)]5-NHMe and 11mer peptide with a Thr(DA) in the center of the sequence contained anti-parallel β-sheet structure and formed polydiacetylene of high degree of polymerization with high conversion during the cleavage process of the peptide from resin in the solution. This result indicated that the preorganization of the peptide through the β-sheet formation was necessary for the polymerization of diacetylene group. Thus, the β-sheet motif was effective template for the polymerization of diacetylene.

  1. Reversibility of crumpling on compressed thin sheets: reversibility of crumpling.

    PubMed

    Pocheau, Alain; Roman, Benoit

    2014-04-01

    Compressing thin sheets usually yields the formation of singularities which focus curvature and stretching on points or lines. In particular, following the common experience of crumpled paper where a paper sheet is crushed in a paper ball, one might guess that elastic singularities should be the rule beyond some compression level. In contrast, we show here that, somewhat surprisingly, compressing a sheet between cylinders make singularities spontaneously disappear at large compression. This "stress defocusing" phenomenon is qualitatively explained from scale-invariance and further linked to a criterion based on a balance between stretching and curvature energies on defocused states. This criterion is made quantitative using the scalings relevant to sheet elasticity and compared to experiment. These results are synthesized in a phase diagram completed with plastic transitions and buckling saturation. They provide a renewed vision of elastic singularities as a thermodynamic condensed phase where stress is focused, in competition with a regular diluted phase where stress is defocused. The physical differences between phases is emphasized by determining experimentally the mechanical response when stress is focused or defocused and by recovering the corresponding scaling laws. In this phase diagram, different compression routes may be followed by constraining differently the two principal curvatures of a sheet. As evidenced here, this may provide an efficient way of compressing a sheet that avoids the occurrence of plastic damages by inducing a spontaneous regularization of geometry and stress.

  2. A numerical method for vortex sheet roll-up

    NASA Technical Reports Server (NTRS)

    Krasny, R.

    1986-01-01

    The problem of computing vortex sheet roll-up from periodic analytic initial data is studied. Previous theoretical and numerical work is reviewed. Computational difficulties arising from ill posedness and singularity formation are discussed. A desingularization method is proposed to diminish these difficulties. Computations indicate that this approach converges past the time at which previous numerical investigations have failed to converge.

  3. Writing by Number: Teaching Students to Read the Balance Sheet.

    ERIC Educational Resources Information Center

    Cross, Mary

    1990-01-01

    Describes an assignment in which students write a short memo report analyzing and comparing both what a company says in its annual report and what its balance sheet shows. Describes four simple mathematical formulas students can use to quickly diagnose a company's financial health. Appends a sample of the short report format. (RS)

  4. Microcomponent chemical process sheet architecture

    DOEpatents

    Wegeng, R.S.; Drost, M.K.; Call, C.J.; Birmingham, J.G.; McDonald, C.E.; Kurath, D.E.; Friedrich, M.

    1998-09-22

    The invention is a microcomponent sheet architecture wherein macroscale unit processes are performed by microscale components. The sheet architecture may be a single laminate with a plurality of separate microcomponent sections or the sheet architecture may be a plurality of laminates with one or more microcomponent sections on each laminate. Each microcomponent or plurality of like microcomponents perform at least one chemical process unit operation. A first laminate having a plurality of like first microcomponents is combined with at least a second laminate having a plurality of like second microcomponents thereby combining at least two unit operations to achieve a system operation. 26 figs.

  5. Microcomponent chemical process sheet architecture

    DOEpatents

    Wegeng, Robert S.; Drost, M. Kevin; Call, Charles J.; Birmingham, Joseph G.; McDonald, Carolyn Evans; Kurath, Dean E.; Friedrich, Michele

    1998-01-01

    The invention is a microcomponent sheet architecture wherein macroscale unit processes are performed by microscale components. The sheet architecture may be a single laminate with a plurality of separate microcomponent sections or the sheet architecture may be a plurality of laminates with one or more microcomponent sections on each laminate. Each microcomponent or plurality of like microcomponents perform at least one chemical process unit operation. A first laminate having a plurality of like first microcomponents is combined with at least a second laminate having a plurality of like second microcomponents thereby combining at least two unit operations to achieve a system operation.

  6. Current sheets in solar flares

    NASA Technical Reports Server (NTRS)

    Priest, E. R.

    1985-01-01

    Numerical simulations of current sheets in solar flares are described, including new features such as the presence of a shock in Petschek's mechanism and impulsive burst-like reconnection due to secondary tearing and coalescence. The general properties of magnetic reconnection are discussed in connection with the basic requirements of numerical current sheet models. Emphasis is given to the need for realistic criteria for energy balance, the Lundquist number, and line tying in calculations of tearing and reconnection modes. The need for analytical models of current sheet processes to compare with the numerical simulations is also stressed.

  7. Selectively reflective transparent sheets

    NASA Astrophysics Data System (ADS)

    Waché, Rémi; Florescu, Marian; Sweeney, Stephen J.; Clowes, Steven K.

    2015-08-01

    We investigate the possibility to selectively reflect certain wavelengths while maintaining the optical properties on other spectral ranges. This is of particular interest for transparent materials, which for specific applications may require high reflectivity at pre-determined frequencies. Although there exist currently techniques such as coatings to produce selective reflection, this work focuses on new approaches for mass production of polyethylene sheets which incorporate either additives or surface patterning for selective reflection between 8 to 13 μ m. Typical additives used to produce a greenhouse effect in plastics include particles such as clays, silica or hydroxide materials. However, the absorption of thermal radiation is less efficient than the decrease of emissivity as it can be compared with the inclusion of Lambertian materials. Photonic band gap engineering by the periodic structuring of metamaterials is known in nature for producing the vivid bright colors in certain organisms via strong wavelength-selective reflection. Research to artificially engineer such structures has mainly focused on wavelengths in the visible and near infrared. However few studies to date have been carried out to investigate the properties of metastructures in the mid infrared range even though the patterning of microstructure is easier to achieve. We present preliminary results on the diffuse reflectivity using FDTD simulations and analyze the technical feasibility of these approaches.

  8. Latent TGF-[beta] structure and activation

    SciTech Connect

    Shi, Minlong; Zhu, Jianghai; Wang, Rui; Chen, Xing; Mi, Lizhi; Walz, Thomas; Springer, Timothy A.

    2011-09-16

    Transforming growth factor (TGF)-{beta} is stored in the extracellular matrix as a latent complex with its prodomain. Activation of TGF-{beta}1 requires the binding of {alpha}v integrin to an RGD sequence in the prodomain and exertion of force on this domain, which is held in the extracellular matrix by latent TGF-{beta} binding proteins. Crystals of dimeric porcine proTGF-{beta}1 reveal a ring-shaped complex, a novel fold for the prodomain, and show how the prodomain shields the growth factor from recognition by receptors and alters its conformation. Complex formation between {alpha}v{beta}6 integrin and the prodomain is insufficient for TGF-{beta}1 release. Force-dependent activation requires unfastening of a 'straitjacket' that encircles each growth-factor monomer at a position that can be locked by a disulphide bond. Sequences of all 33 TGF-{beta} family members indicate a similar prodomain fold. The structure provides insights into the regulation of a family of growth and differentiation factors of fundamental importance in morphogenesis and homeostasis.

  9. Two-dimensional thin-layer chromatography for simultaneous detection of bacterial beta-lactam acylases and beta-lactamases.

    PubMed Central

    Chen, K C

    1986-01-01

    A rapid and specific procedure was developed for the simultaneous detection of bacterial acylases and beta-lactamases, using ampicillin and cephalexin as substrates. Bacterial suspensions from agar plates were incubated separately with each beta-lactam substrate for 1 h at 37 degrees C. The supernatant of the reaction mixture was dansylated, and the dansyl derivatives were separated by two-dimensional thin-layer chromatography on polyamide sheets. The end products resulting from acylase hydrolysis, including the intact beta-lactam nucleus, 6-aminopenicillanic acid or 7-aminodeacetoxycephalosporanic acid, and the acyl side chain acid, D-(-)-alpha-aminophenylacetic acid, and the end product resulting from beta-lactamase hydrolysis (D-phenylglycylpenicilloic acid or D-phenylglycyldeacetoxycephalosporoic acid) were separated from each unhydrolyzed substrate and amino acids by this procedure. The presence of the intact beta-lactam nucleus in the reaction mixture is the indication of acylase activity. This method is sensitive and reproducible and has been successfully applied to screening for acylase activity in a variety of bacteria. It may be pharmaceutically useful for identifying organisms capable of removing the acyl side chain from naturally occurring beta-lactam antibiotics such as penicillin G, penicillin V, and cephalosporin C for production of the beta-lactam nuclei which serve as the starting materials for semisynthetic beta-lactam antibiotics. Images PMID:3539008

  10. Current Sheet Properties and Dynamics During Sympathetic Breakout Eruptions

    NASA Astrophysics Data System (ADS)

    Lynch, B. J.; Edmondson, J. K.

    2013-12-01

    We present the continued analysis of the high-resolution 2.5D MHD simulations of sympathetic magnetic breakout eruptions from a pseudostreamer source region. We examine the generation of X- and O-type null points during the current sheet tearing and track the magnetic island formation and evolution during periods of reconnection. The magnetic breakout eruption scenario forms an overlying 'breakout' current sheet that evolves slowly and removes restraining flux from above the sheared field core that will eventually become the center of the erupting flux rope-like structure. The runaway expansion from the expansion-breakout reconnection positive feedback enables the formation of the second, vertical/radial current sheet underneath the rising sheared field core as in the standard CHSKP eruptive flare scenario. We will examine the flux transfer rates through the breakout and flare current sheets and compare the properties of the field and plasma inflows into the current sheets and the reconnection jet outflows into the flare loops and flux rope ejecta.

  11. Visco-resistive tearing in thin current sheets.

    NASA Astrophysics Data System (ADS)

    Velli, M. M. C.; Tenerani, A.; Rappazzo, A. F.; Pucci, F.

    2014-12-01

    How fast magnetic energy release is triggered and occurs in high Lundquist (S) and high Reynolds number ( R ) plasmas such as that of the solar corona is a fundamental problem for understanding phenomena ranging from coronal heating to flares and CMEs. Diffusion or collisional reconnection driven by macroscopic flows in quasi-steady Sweet-Parker (SP) current sheets are processes far too slow to fit observational data. Spontaneous reconnection, driven by the onset of the tearing instability inside current sheets, provides an alternative paradigm to SP reconnection. Nevertheless, as long as macroscopic current layers are considered, the growth of such an instability is also a slow process. Recently it has been shown that SP current sheets are rapidly unstable in high S plasmas, indeed have a growth rate diverging with increasing S. It has been suggested that such instabilities are triggered during the nonlinear stage of the primary tearing instability of a macroscopic layer. The formation of plasmoids in this presumed SP sheet speeds up the reconnection rate to ideal values. Recently, we have suggested that SP sheets can not be realized in quasi-ideal plasmas, and that the plasmoid instability is triggered on a much larger scale (i.e. with current sheets having a much larger ration of thickness to length than SP). Here we present a linear parametric study of the tearing instability for a Harris current sheet, while taking into account both viscosity and current sheets of variable aspect ratios. The present study shows that an explosive growth of the reconnection rate may be reached during the linear stage, once a critical width of the current layer is reached. In the absence of a strong guide field this depends on viscosity and a range of critical aspect ratios can be found for different values of S, R, or S and Prandtl number.

  12. Looking for a generic inhibitor of amyloid-like fibril formation among flavone derivatives

    PubMed Central

    Šneideris, Tomas; Baranauskienė, Lina; Cannon, Jonathan G.; Rutkienė, Rasa; Meškys, Rolandas

    2015-01-01

    A range of diseases is associated with amyloid fibril formation. Despite different proteins being responsible for each disease, all of them share similar features including beta-sheet-rich secondary structure and fibril-like protein aggregates. A number of proteins can form amyloid-like fibrils in vitro, resembling structural features of disease-related amyloids. Given these generic structural properties of amyloid and amyloid-like fibrils, generic inhibitors of fibril formation would be of interest for treatment of amyloid diseases. Recently, we identified five outstanding inhibitors of insulin amyloid-like fibril formation among the pool of 265 commercially available flavone derivatives. Here we report testing of these five compounds and of epi-gallocatechine-3-gallate (EGCG) on aggregation of alpha-synuclein and beta-amyloid. We used a Thioflavin T (ThT) fluorescence assay, relying on halftimes of aggregation as the measure of inhibition. This method avoids large numbers of false positive results. Our data indicate that four of the five flavones and EGCG inhibit alpha-synuclein aggregation in a concentration-dependent manner. However none of these derivatives were able to increase halftimes of aggregation of beta-amyloid. PMID:26421240

  13. Characterization of Hydrogels Formed via Intramolecular Folding and Consequent Self-Assembly of Beta-HAIRPIN Peptides

    NASA Astrophysics Data System (ADS)

    Ozbas, Bulent; Pakstis, Lisa; Pochan, Darrin J.; Rajagopal, Karthikan; Gill, Juliana; Schneider, Joel P.

    2003-03-01

    Stimuli-responsive and biocompatible networks formed via self-assembly serve great opportunities in tissue engineering and drug delivery applications. In this work we present the formation of hydrogels via the intramolecular folding and consequent self-assembly of 20 aminoacid long beta-Hairpin peptide molecules. These hairpin molecules are amphiphilic in nature with an alternating sequence of hydrophobic valine and hydrophilic lysine amino acids. These molecules are found to form hydrogels with a unique microstructure and nanostructure at different physical condition at low peptide concentrations ( ˜ 1 wt %). However, gelation is observed at high pH values ( ˜9) and at high salt concentrations ( ˜150 mM) where beta-sheet secondary structure due to hairpin folding is observed. The intimate relationship between beta-Hairpin molecule turn sequence and the consequent materials properties will be discussed. LSCM data reveals that hydrogel structure is heterogeneous at the microscale with water channels in the order of 10 μm. Cryo-TEM technique shows that the network is consists of interconnected fibrillar/tubular networks. The viscoelastic properties of the hydrogels, as measured by rheology. Importantly, the gel is also reversible with pH, returning to a viscosity of water with a drop in pH that unfolds, and disassembles, the hairpin molecules.

  14. Arachidonic acid mediates the formation of abundant alpha-helical multimers of alpha-synuclein

    NASA Astrophysics Data System (ADS)

    Iljina, Marija; Tosatto, Laura; Choi, Minee L.; Sang, Jason C.; Ye, Yu; Hughes, Craig D.; Bryant, Clare E.; Gandhi, Sonia; Klenerman, David

    2016-09-01

    The protein alpha-synuclein (αS) self-assembles into toxic beta-sheet aggregates in Parkinson’s disease, while it is proposed that αS forms soluble alpha-helical multimers in healthy neurons. Here, we have made αS multimers in vitro using arachidonic acid (ARA), one of the most abundant fatty acids in the brain, and characterized them by a combination of bulk experiments and single-molecule Fӧrster resonance energy transfer (sm-FRET) measurements. The data suggest that ARA-induced oligomers are alpha-helical, resistant to fibril formation, more prone to disaggregation, enzymatic digestion and degradation by the 26S proteasome, and lead to lower neuronal damage and reduced activation of microglia compared to the oligomers formed in the absence of ARA. These multimers can be formed at physiologically-relevant concentrations, and pathological mutants of αS form less multimers than wild-type αS. Our work provides strong biophysical evidence for the formation of alpha-helical multimers of αS in the presence of a biologically relevant fatty acid, which may have a protective role with respect to the generation of beta-sheet toxic structures during αS fibrillation.

  15. Cartilage engineering using chondrocyte cell sheets and its application in reconstruction of microtia.

    PubMed

    Zhou, Libin; Ding, Ruiying; Li, Baowei; Han, Haolun; Wang, Hongnan; Wang, Gang; Xu, Bingxin; Zhai, Suoqiang; Wu, Wei

    2015-01-01

    The imperfections of scaffold materials have hindered the clinical application of cartilage tissue engineering. The recently developed cell-sheet technique is adopted to engineer tissues without scaffold materials, thus is considered being potentially able to overcome the problems concerning the scaffold imperfections. This study constructed monolayer and bilayer chondrocyte cell sheets and harvested the sheets with cell scraper instead of temperature-responsive culture dishes. The properties of the cultured chondrocyte cell sheets and the feasibility of cartilage engineering using the chondrocyte cell sheets was further investigated via in vitro and in vivo study. Primary extracellular matrix (ECM) formation and type II collagen expression was detected in the cell sheets during in vitro culture. After implanted into nude mice for 8 weeks, mature cartilage discs were harvested. The morphology of newly formed cartilage was similar in the constructs originated from monolayer and bilayer chondrocyte cell sheet. The chondrocytes were located within evenly distributed ovoid lacunae. Robust ECM formation and intense expression of type II collagen was observed surrounding the evenly distributed chondrocytes in the neocartilages. Biochemical analysis showed that the DNA contents of the neocartilages were higher than native human costal cartilage; while the contents of the main component of ECM, glycosaminoglycan and hydroxyproline, were similar to native human costal cartilage. In conclusion, the chondrocyte cell sheet constructed using the simple and low-cost technique is basically the same with the cell sheet cultured and harvested in temperature-responsive culture dishes, and can be used for cartilage tissue engineering.

  16. Industrial Stormwater Fact Sheet Series

    EPA Pesticide Factsheets

    Fact sheets for the industrial sectors regulated by the MSGP. Each describes the types of facilities included in the sector, typical pollutants associated with the sector, and types of stormwater control measures used to minimize pollutant discharge.

  17. 2007 Swimming Season Fact Sheets

    EPA Pesticide Factsheets

    To help beachgoers make informed decisions about swimming at U.S. beaches, EPA annually publishes state-by-state data about beach closings and advisories for the previous year's swimming season. These fact sheets summarize that information by state.

  18. 2006 Swimming Season Fact Sheets

    EPA Pesticide Factsheets

    To help beachgoers make informed decisions about swimming at U.S. beaches, EPA annually publishes state-by-state data about beach closings and advisories for the previous year's swimming season. These fact sheets summarize that information by state.

  19. Analysis of a Sheet Silicate.

    ERIC Educational Resources Information Center

    Adams, J. M.; Evans, S.

    1980-01-01

    Describes a student project in analytical chemistry using sheet silicates. Provides specific information regarding the use of phlogopite in an experiment to analyze samples for silicon, aluminum, magnesium, iron, potassium, and fluoride. (CS)

  20. Palaeoclimate science: Pulsating ice sheet

    NASA Astrophysics Data System (ADS)

    Vieli, Andreas

    2017-02-01

    During the last ice age, huge numbers of icebergs were episodically discharged from an ice sheet that covered North America. Numerical modelling suggests that these events resulted from a conceptually simple feedback cycle. See Letter p.332

  1. 2009 Swimming Season Fact Sheets

    EPA Pesticide Factsheets

    To help beachgoers make informed decisions about swimming at U.S. beaches, EPA annually publishes state-by-state data about beach closings and advisories for the previous year's swimming season. These fact sheets summarize that information by state.

  2. 2010 Swimming Season Fact Sheets

    EPA Pesticide Factsheets

    To help beachgoers make informed decisions about swimming at U.S. beaches, EPA annually publishes state-by-state data about beach closings and advisories for the previous year's swimming season. These fact sheets summarize that information by state.

  3. Concentrating Solar Power (Fact Sheet)

    SciTech Connect

    Not Available

    2010-08-01

    Fact sheet describing the overall capabilities of the NREL CSP Program: collector/receiver characterization, advanced reflector and absorber materials, thermal storage and advanced heat transfer fluids, and CSP modeling and analysis.

  4. 2008 Swimming Season Fact Sheets

    EPA Pesticide Factsheets

    To help beachgoers make informed decisions about swimming at U.S. beaches, EPA annually publishes state-by-state data about beach closings and advisories for the previous year's swimming season. These fact sheets summarize that information by state.

  5. Measurements and Characterization (Fact Sheet)

    SciTech Connect

    Not Available

    2011-06-01

    Capabilities fact sheet for the National Center for Photovoltaics: Measurements and Characterization that includes scope, core competencies and capabilities, and contact/web information for Analytical Microscopy, Electro-Optical Characterization, Surface Analysis, and Cell and Module Performance.

  6. Subwavelength Imaging Using Conducting Sheets

    NASA Astrophysics Data System (ADS)

    Monzon, Cesar

    2009-05-01

    Here we demonstrate that, paradoxically, subwavelength imaging can be produced by purely resistive means. Space acts like a low pass filter for highly evanescent field components, and if a sheet or thin layer of imperfectly conducting material is placed adjacent to a source, such that the layer overcomes the larger impedance of the spatial low pass filter, no relative attenuation of evanescent components is experienced at the location of the sheet. This results in near-field subwavelength imaging, which also holds for reactive sheets. The conducting layer enables us to trade definition for amplitude. Impedance sheets are commonplace in radio frequencies or microwaves, hence the phenomenon identified here is widespread, and can be extended into the IR or optical region, as well as to other areas of physics where wave motion exists.

  7. Theoretical modeling of the plasma-assisted catalytic growth and field emission properties of graphene sheet

    SciTech Connect

    Sharma, Suresh C.; Gupta, Neha

    2015-12-15

    A theoretical modeling for the catalyst-assisted growth of graphene sheet in the presence of plasma has been investigated. It is observed that the plasma parameters can strongly affect the growth and field emission properties of graphene sheet. The model developed accounts for the charging rate of the graphene sheet; number density of electrons, ions, and neutral atoms; various elementary processes on the surface of the catalyst nanoparticle; surface diffusion and accretion of ions; and formation of carbon-clusters and large graphene islands. In our investigation, it is found that the thickness of the graphene sheet decreases with the plasma parameters, number density of hydrogen ions and RF power, and consequently, the field emission of electrons from the graphene sheet surface increases. The time evolution of the height of graphene sheet with ion density and sticking coefficient of carbon species has also been examined. Some of our theoretical results are in compliance with the experimental observations.

  8. Energy information sheets, July 1998

    SciTech Connect

    1998-07-01

    The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the public. The Energy Information Sheets was developed to provide general information on various aspects of fuel production, prices, consumption, and capability. Additional information on related subject matter can be found in other Energy Information Administration (EIA) publications as referenced at the end of each sheet.

  9. Electromechanical resonators from graphene sheets.

    PubMed

    Bunch, J Scott; van der Zande, Arend M; Verbridge, Scott S; Frank, Ian W; Tanenbaum, David M; Parpia, Jeevak M; Craighead, Harold G; McEuen, Paul L

    2007-01-26

    Nanoelectromechanical systems were fabricated from single- and multilayer graphene sheets by mechanically exfoliating thin sheets from graphite over trenches in silicon oxide. Vibrations with fundamental resonant frequencies in the megahertz range are actuated either optically or electrically and detected optically by interferometry. We demonstrate room-temperature charge sensitivities down to 8 x 10(-4) electrons per root hertz. The thinnest resonator consists of a single suspended layer of atoms and represents the ultimate limit of two-dimensional nanoelectromechanical systems.

  10. Energy information sheets, September 1996

    SciTech Connect

    1996-09-01

    The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the public. The Energy Information Sheets was developed to provide general information on various aspects of fuel production, prices, consumption, and capability. Additional information on related subject matter can be found in other Energy Information Administration (EIA) publications as referenced at the end of each sheet.

  11. Synchrotron-based Infrared and X-ray Imaging Shows Focalized Accumulation of Cu and Zn Co-localized With Beta-amyloid Deposits in Alzheimer's Disease

    SciTech Connect

    Miller,L.; Wang, Q.; Telivala, T.; Smith, R.; Lanzirotti, A.; Miklossy, J.

    2006-01-01

    Alzheimer's disease (AD) is characterized by the misfolding and plaque-like accumulation of a naturally occurring peptide in the brain called amyloid beta (Abeta). Recently, this process has been associated with the binding of metal ions such as iron (Fe), copper (Cu), and zinc (Zn). It is thought that metal dyshomeostasis is involved in protein misfolding and may lead to oxidative stress and neuronal damage. However, the exact role of the misfolded proteins and metal ions in the degenerative process of AD is not yet clear. In this study, we used synchrotron Fourier transform infrared micro-spectroscopy (FTIRM) to image the in situ secondary structure of the amyloid plaques in brain tissue of AD patients. These results were spatially correlated with metal ion accumulation in the same tissue sample using synchrotron X-ray fluorescence (SXRF) microprobe. For both techniques, a spatial resolution of 5-10 microm was achieved. FTIRM results showed that the amyloid plaques have elevated beta-sheet content, as demonstrated by a strong amide I absorbance at 1625cm(-1). Using SXRF microprobe, we find that AD tissue also contains 'hot spots' of accumulated metal ions, specifically Cu and Zn, with a strong spatial correlation between these two ions. The 'hot spots' of accumulated Zn and Cu were co-localized with beta-amyloid plaques. Thus for the first time, a strong spatial correlation has been observed between elevated beta-sheet content in Abeta plaques and accumulated Cu and Zn ions, emphasizing an association of metal ions with amyloid formation in AD.

  12. Dynamic behavior of liquid sheets

    NASA Astrophysics Data System (ADS)

    Mansour, Adel; Chigier, Norman

    1991-12-01

    An experiment was conducted to study the aerodynamic instability of liquid sheets issuing from a two-dimensional air-assisted nozzle. Detailed measurements of the frequency of oscillation of the liquid sheet have been made. The measured vibrational frequencies were then correlated with the resulting spray angle. It was shown that the liquid sheet oscillations are dynamically similar to that of hard spring systems. For each air pressure, three distinct modes of breakup are distinguished. At low liquid flow rates, both the sinusoidal and the dilational modes are superimposed on the liquid sheet. With a further increase in liquid flow rate, the liquid sheet oscillations mainly become of the dilational type. It was also shown that the effect of introducing air in the nozzle is similar to the effect of inducing forced vibrations on the nozzle jaws. Thus, for each air flow rate, there is a specific vibration frequency for the nozzle. The frequency of these vibrations is proportional to the air velocity. As the liquid sheet natural frequency approaches that of the nozzle, resonance is established. At resonance, the maximum spray angle is achieved.

  13. FDTD modeling of thin impedance sheets

    NASA Technical Reports Server (NTRS)

    Luebbers, Raymond J.; Kunz, Karl S.

    1991-01-01

    Thin sheets of resistive or dielectric material are commonly encountered in radar cross section calculations. Analysis of such sheets is simplified by using sheet impedances. In this paper it is shown that sheet impedances can be modeled easily and accurately using Finite Difference Time Domain (FDTD) methods.

  14. Cryosphere: Warming ocean erodes ice sheets

    NASA Astrophysics Data System (ADS)

    Kusahara, Kazuya

    2016-01-01

    Antarctic ice sheets are a key player in sea-level rise in a warming climate. Now an ice-sheet modelling study clearly demonstrates that an Antarctic ice sheet/shelf system in the Atlantic Ocean will be regulated by the warming of the surrounding Southern Ocean, not by marine-ice-sheet instability.

  15. Journal Sheets in the Choral Rehearsal.

    ERIC Educational Resources Information Center

    Kassler, David J.

    2001-01-01

    Discusses the use of journal sheets with choral students. Addresses the benefits of journal sheets, such as providing a means to determine the level of students' critical thinking skills or as a way to reinforce concepts. Includes a copy of a journal sheet and journal sheet responses from choral students. (CMK)

  16. Immunolocalization of alpha-keratins and feather beta-proteins in feather cells and comparison with the general process of cornification in the skin of mammals.

    PubMed

    Alibardi, L

    2013-03-01

    The maturation of the corneous material of feathers is a special case of cornification in vertebrate epidermis and is believed to occur mainly by the accumulation of small proteins of about 100 amino acids and a central beta-pleated sheet region known as feather keratins. The present immunocytochemical study carried out using double-labeling immunogold shows that a small amount of alpha-keratins of intermediate filament type form the early keratin clumps in barb and barbule cells. These initial nuclei of formation of corneous material are rapidly coated by the deposition of large amounts of small feather keratin-associated beta-proteins (feather keratins). The latter proteins turn the keratin bundles of barb and barbule cells into a compact and apparently amorphous mass of corneous material where no sign of intermediate filaments are seen. Feather beta-proteins however form an irregular filamentous network of 2-3nm thick electron-pale filaments and produce the characteristic feather X-ray pattern due to their prevalent amount over any other protein present in feather cells. The modality of cornification in feathers is discussed in relation to the process of formation of corneous material in the skin of vertebrates in general that occurs by the association of intermediate filament proteins and keratin-associated proteins.

  17. Analysis of the distributed computing approach applied to the folding of a small beta peptide.

    PubMed

    Paci, Emanuele; Cavalli, Andrea; Vendruscolo, Michele; Caflisch, Amedeo

    2003-07-08

    In the recently proposed distributed computing approach to protein folding a very large number of short independent simulations is performed. Using this method, folding events on a time scale orders of magnitude shorter than the experimental one have been reported. However, it has also been observed that the folding process is not an elementary kinetic step and that the presence of initial lag phases can bias short simulations toward atypical pathways. We study here a 20-residue three-stranded antiparallel beta-sheet peptide whose equilibrium properties can be characterized by atomistic molecular dynamics simulations. We found that the folding rate of this peptide is estimated correctly by the distributed computing approach when trajectories > approximately 1/100 of the equilibrium folding time are considered. We also found that the fastest folding events occur through high-energy pathways, which are unlikely under equilibrium conditions. These very fast folding pathways do not relax within the equilibrium denatured state that is stabilized by the transient presence of both native and non-native interactions, and they are characterized by the nearly simultaneous formation of the two beta-hairpins and a very small number of non-native contacts.

  18. FDTD modeling of thin impedance sheets

    NASA Technical Reports Server (NTRS)

    Luebbers, Raymond; Kunz, Karl

    1991-01-01

    Thin sheets of resistive or dielectric material are commonly encountered in radar cross section calculations. Analysis of such sheets is simplified by using sheet impedances. It is shown that sheet impedances can be modeled easily and accurately using Finite Difference Time Domain (FDTD) methods. These sheets are characterized by a discontinuity in the tangential magnetic field on either side of the sheet but no discontinuity in tangential electric field. This continuity, or single valued behavior of the electric field, allows the sheet current to be expressed in terms of an impedance multiplying this electric field.

  19. The selectivity of beta-adrenoceptor antagonists at the human beta1, beta2 and beta3 adrenoceptors.

    PubMed

    Baker, Jillian G

    2005-02-01

    Beta-adrenoceptor antagonists ("beta-blockers") are one of the most widely used classes of drugs in cardiovascular medicine (hypertension, ischaemic heart disease and increasingly in heart failure) as well as in the management of anxiety, migraine and glaucoma. Where known, the mode of action in cardiovascular disease is from antagonism of endogenous catecholamine responses in the heart (mainly at beta1-adrenoceptors), while the worrisome side effects of bronchospasm result from airway beta2-adrenoceptor blockade. The aim of this study was to determine the selectivity of beta-antagonists for the human beta-adrenoceptor subtypes. (3)H-CGP 12177 whole cell-binding studies were undertaken in CHO cell lines stably expressing either the human beta1-, beta2- or the beta3-adrenoceptor in order to determine the affinity of ligands for each receptor subtype in the same cell background. In this study, the selectivity of well-known subtype-selective ligands was clearly demonstrated: thus, the selective beta1 antagonist CGP 20712A was 501-fold selective over beta2 and 4169-fold selective over beta3; the beta2-selective antagonist ICI 118551 was 550- and 661-fold selective over beta1 and beta3, respectively, and the selective beta3 compound CL 316243 was 10-fold selective over beta2 and more than 129-fold selective over beta1. Those beta2-adrenoceptor agonists used clinically for the treatment of asthma and COPD were beta2 selective: 29-, 61- and 2818-fold for salbutamol, terbutaline and salmeterol over beta1, respectively. There was little difference in the affinity of these ligands between beta1 and beta3 adrenoceptors. The clinically used beta-antagonists studied ranged from bisoprolol (14-fold beta1-selective) to timolol (26-fold beta2-selective). However, the majority showed little selectivity for the beta1- over the beta2-adrenoceptor, with many actually being more beta2-selective. This study shows that the beta1/beta2 selectivity of most clinically used beta-blockers is

  20. Preparation of creep data sheet: Material strength data sheet

    NASA Astrophysics Data System (ADS)

    Tanaka, Chiaki; Yagi, Koichi; Ikeda, Sadao; Ito, Hiroshi; Baba, Eiji; Shimizu, Masaru; Tanaka, Hideo; Yokokawa, Kenji; Nagai, Hideo; Kanamaru, Osamu

    1993-01-01

    Continuing from the first and the second term, creep rupture data sheet on metals for high temperatures was continued targeting for 100,000 hours. Creep strain data sheet for elastic analysis, conceived in the second term was carried out this term. Additionally, research was planned into the Cr group steel, which is increasingly in demand for high temperature equipment, and material sampling and testing commenced accordingly. In 1986, the creep data sheet (B Version) was published for the first time, including the creep rupture data exceeding final target of 100,000 hours. Since then, B versions were published on 12 different materials this term. There has been much research using the data from creep data sheets and test samples, including creep strain characteristics, stress relaxation characteristics, creep rupture characteristics and life estimate, with substantial results. In the creep test technology aiming for highly reliable data, deterioration factors of thermocouples were investigated. The results from creep data sheets and related research contributed to improvement in strength reliability of metals at high temperatures.

  1. Anti-beta2-glycoprotein I (beta2GPI) monoclonal antibodies with lupus anticoagulant-like activity enhance the beta2GPI binding to phospholipids.

    PubMed Central

    Takeya, H.; Mori, T.; Gabazza, E. C.; Kuroda, K.; Deguchi, H.; Matsuura, E.; Ichikawa, K.; Koike, T.; Suzuki, K.

    1997-01-01

    beta2-Glycoprotein I (beta2GPI), a plasma glycoprotein with phospholipid-binding property, is known to be the actual target antigen for autoimmune type anticardiolipin antibodies (aCLs). Certain groups of aCLs (anti-beta2GPI antibodies) exert lupus anticoagulant (LA) activity and perturb the function of vascular endothelial cells. This investigation aimed at highlighting some insights into the molecular basis by which aCLs exert their biological effects by using anti-beta2GPI mAbs with well-characterized epitopes from mice and from patients with antiphospholipid syndrome. Anti-beta2GPI mAbs directed against the third domain (Cof-20 and Cof-22) and fourth domain (Cof-21, EY1C8, and EY2C9) of beta2GPI inhibited the thrombin generation induced by Russell's viper venom in diluted plasma and that induced by the prothrombinase complex reconstituted with purified clotting factors. This anticoagulant activity was abrogated in the presence of an excess amount of phospholipids, thus resembling the LA activity. In stark contrast, anti-beta2GPI mAbs directed against the fifth domain and the carboxy-terminal region of the fourth domain showed no LA-like activity. These findings suggest that the LA activity of anti-beta2GPI antibodies depends on their epitope specificity. Experiments carried out to clarify the mechanism of the LA activity showed that anti-beta2GPI mAbs with LA-like activity, but not those without this effect, enhance the beta2GPI binding to phospholipids. In addition, the F(ab')2 fragment, but not the Fab' fragment, of the anti-beta2GPI mAbs was found to enhance the LA activity and the beta2GPI binding to phospholipids, suggesting that anti-beta2GPI antibodies induce formation of multiple complexes of beta2GPI on the surface of phospholipids because of their bivalent property. This clustering of beta2GPI molecules induced by anti-beta2GPI antibodies, probably because of their multivalent property and epitope specificity, might hinder the lateral mobility and

  2. A facile liquid phase exfoliation method to prepare graphene sheets with different sizes expandable graphite

    SciTech Connect

    Zhou, Keqing; Shi, Yongqian; Jiang, Saihua; Song, Lei; Hu, Yuan; Gui, Zhou

    2013-09-01

    Graphical abstract: - Highlights: • This study presented a novel method for the production of high-quality graphene sheets through the exfoliation of Li-intercalated EG with sonication. • The quality of the graphene sheets produced from different sizes EG was compared for the first time and the formation mechanism was discussed. • The graphene sheets obtained from the small size EG have less layers than the large size EG. - Abstract: In this work, graphene sheets suspension were synthesized directly from expandable graphite (EG) via an intercalation and exfoliation pathway using n-butyl lithium as the intercalating agent, water and N,N-dimethylformamide (DMF) as the exfoliating agent. The quality of the graphene sheets produced from different sizes EG was compared and the formation mechanism was discussed. The formation of the graphene sheets and its formation mechanism were confirmed by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area electron diffraction (SAED), Raman spectroscopy measurement, inductively coupled plasma atomic emission spectrometry (ICP-AES) and thermogravimetric analysis (TGA). The graphene sheets obtained from the small size EG have less layers than the large size EG.

  3. Modeling the formation of secondary organic aerosol. 1. Application of theoretical principles to measurements obtained in the alpha-pinene/, beta-pinene/, sabinene/, delta3-carene/, and cyclohexane/ozone systems.

    PubMed

    Pankow, J F; Seinfeld, J H; Asher, W E; Erdakos, G B

    2001-03-15

    , similarly low-volatility compounds. This was overcome in part by using the G/P data from the alpha-pinene and cyclohexene experiments to determine pL(degrees) values for use (along with a set of 14 other independent polar compounds) in calculating UNIFAC vapor pressure parameters that were, in turn, used to estimate all of the needed pL(degrees) values. The significant degree of resultant circularity in the calculations for alpha-pinene and cyclohexene helped lead to the good agreement that was found between the Yi values predicted by the model, and those measured experimentally for those two compounds. However, the model was also able to predict the aerosol yield values from beta-pinene, sabinene, and delta3-carene, for which there was significatly less circularity in the calculations, thereby providing evidence supporting the idea that given the correct input information, SOA formation can in fact be accurately modeled as a multicomponent condensation process.

  4. Horizontal electromagnetic casting of thin metal sheets

    DOEpatents

    Hull, John R.; Lari, Robert J.; Praeg, Walter F.; Turner, Larry R.

    1988-01-01

    Thin metal sheets are cast by magnetically suspending molten metal deposited within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled to form a solid metal sheet. Magnetic flux increases as the molten metal sheet moves downward and decreases as the molten metal sheet moves upward to stabilize the sheet and maintain it in equilibrium as it is linearly displaced and solidified by cooling gases. A conducting shield is electrically coupled to the molten metal sheet by means of either metal sheet engaging rollers or brushes on the solidified metal, and by means of an electrode in the vessel containing the molten metal thereby providing a return path for the eddy currents induced in the metal sheet by the AC coil generated magnetic flux. Variation in the geometry of the conducting shield allows the magnetic flux between the metal sheet and the conducting shield to be varied and the thickness in surface quality of the metal sheet to be controlled. Side guards provide lateral containment for the molten metal sheet and stabilize and shape the magnetic field while a leader sheet having electromagnetic characteristics similar to those of the metal sheet is used to start the casting process and precedes the molten metal sheet through the magnet and forms a continuous sheet therewith. The magnet may be either U-shaped with a single racetrack coil or may be rectangular with a pair of facing bedstead coils.

  5. Horizontal electromagnetic casting of thin metal sheets

    DOEpatents

    Hull, John R.; Lari, Robert J.; Praeg, Walter F.; Turner, Larry R.

    1987-01-01

    Thin metal sheets are cast by magnetically suspending molten metal deposited within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled to form a solid metal sheet. Magnetic flux increases as the molten metal sheet moves downward and decreases as the molten metal sheet moves upward to stabilize the sheet and maintain it in equilibrium as it is linearly displaced and solidified by cooling gases. A conducting shield is electrically coupled to the molten metal sheet by means of either metal sheet engaging rollers or brushes on the solidified metal, and by means of an electrode in the vessel containing the molten metal thereby providing a return path for the eddy currents induced in the metal sheet by the AC coil generated magnetic flux. Variation in the geometry of the conducting shield allows the magnetic flux between the metal sheet and the conducting shield to be varied and the thickness in surface quality of the metal sheet to be controlled. Side guards provide lateral containment for the molten metal sheet and stabilize and shape the magnetic field while a leader sheet having electromagnetic characteristics similar to those of the metal sheet is used to start the casting process and precedes the molten metal sheet through the magnet and forms a continuous sheet therewith. The magnet may be either U-shaped with a single racetrack coil or may be rectangular with a pair of facing bedstead coils.

  6. Dynamic of Current Sheets and Their Associated Particle Energization

    SciTech Connect

    Li, Hui; Guo, Fan; Makwan, Kirit; Li, Xiaocan; Zhandrin, Vladimir; Daughton, William Scott

    2015-08-19

    Magnetic reconnection in current sheets has relevance to Earth's magnetosphere, solar flares, high-energy astrophysics (pulsar wind nebula (e.g. Crab Nebula), gamma-ray bursts, black hole jets), and laboratory plasma/fusion. Data are shown for several cases with varying values of configuration energy Ec and β. Several conclusions were drawn: Depending on the “configuration energy”, the formation, shape, and lifetime of current sheets can vary. Plasma condition (configuration, β, driving, etc.) strongly affect the efficiency of particle acceleration. For low β and general “configuration energy”, particle heating is expected. For low β, large and long-lived current sheets, it is possible to produce highly non-thermal particles via collisionless plasmoid reconnection.

  7. Younger Dryas interval and outflow from the Laurentide ice sheet

    USGS Publications Warehouse

    Moore, T.C.; Walker, J.C.G.; Rea, David K.; Lewis, C.F.M.; Shane, L.C.K.; Smith, A.J.

    2000-01-01

    A boxmodel of the Great Lakes is used to estimate meltwater flow into the North Atlantic between 8000 and 14,000 calendar years B.P. Controls on the model include the oxygen isotopic composition of meltwaters and lake waters as measured in the shells of ostracodes. Outflow rates are highest when oxygen isotopic values of the lake waters are most negative, denoting a maximum glacial meltwater component. Flow rates reach maximum values before the onset of the Younger Dryas and after it ends. These maxima appear to be correlative with the major meltwater pulses MWP 1A and 1B. Although the resumption of North Atlantic Deep Water formation may be tied to the reduction in ice sheet melting, neither the onset nor the end of the Younger Dryas, as recorded in the Greenland Ice Sheet Project (GISP2) records, appear tied to maxima in meltwater outflow from the Laurentide ice sheet. Copyright 2000 by the American Geophysical Union.

  8. The current-voltage relationship in auroral current sheets

    NASA Technical Reports Server (NTRS)

    Weimer, D. R.; Gurnett, D. A.; Goertz, C. K.; Menietti, J. D.; Burch, J. L.

    1987-01-01

    The current-voltage relation within narrow auroral current sheets is examined through the use of high-resolution data from the high altitude Dynamics Explorer 1 satellite. The north-south perpendicular electric field and the east-west magnetic field are shown for three cases in which there are large amplitude, oppositely directed paired electric fields and narrow current sheets. These data are shown to indicate that there is a linear Ohm's law relationship between the current density and the parallel potential drop within the narrow current sheets. This linear relationship had previously been verified for large-scale auroral formations greater than 20 km wide at the ionosphere. The evidence shown here extends our knowledge down to the scale size of discrete auroral arcs.

  9. MOON for neutrino-less {beta}{beta} decays and {beta}{beta} nuclear matrix elements

    SciTech Connect

    Ejiri, H.

    2009-11-09

    The MOON project aims at spectroscopic 0v{beta}{beta} studies with the v-mass sensitivity of 100-30 meV by measuring two beta rays from {sup 100}Mo and/or {sup 82}Se. The detector is a compact super-module of multi-layer PL scintillator plates. R and D works made by the pro to-type MOON-1 and the small PL plate show the possible energy resolution of around {sigma}{approx}2.2%, as required for the mass sensitivity. Nuclear matrix elements M{sup 2v} for 2v{beta}{beta} are shown to be given by the sum {sigma}{sub L}M{sub k} of the 2v{beta}{beta} matrix elements M{sub k} through intermediate quasi-particle states in the Fermi-surface, where Mi is obtained experimentally by using the GT(J{sup {pi}} = 1{sup +}) matrix elements of M{sub i}(k) and M{sub f}(k) for the successive single-{beta} transitions through the k-th intermediate state.

  10. Beta-Carotene

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Beta-carotene is a pigment that occurs naturally in many photosynthetic plants and organisms and one of the most abundant carotenoids found in human blood. The richest dietary sources of beta-carotene are yellow, orange, and leafy green fruits and vegetables, such as carrots, spinach, sweet potatoes...

  11. Beta blockers in hypertension.

    PubMed

    Thadani, U

    1983-11-10

    Beta-adrenoceptor antagonists are effective in the management of patients with mild-to-moderate hypertension. Noncardioselective agents, cardioselective agents and beta blockers with intrinsic sympathomimetic activity (ISA) are equally effective, provided they are used in equipotent doses. Beta blockers can be used as first-line therapy in the management of hypertension and can be safely combined with diuretics, vasodilators, or both, for a better control of blood pressure. The exact mechanism by which beta blockers decrease blood pressure remains speculative, but they all reduce cardiac output during long-term therapy; drugs with ISA lower cardiac output and heart rate less than do drugs without ISA. Pharmacokinetic properties of beta blockers differ widely; drugs metabolized by the liver have shorter plasma half-lives than drugs primarily excreted by the kidneys. Although many of the side effects of various beta blockers are similar, differences in water and lipid solubility account for a higher incidence of central nervous system side effects with lipid-soluble drugs (such as propranolol and metoprolol) than with hydrophilic drugs (such as atenolol and timolol). The incidence of cold extremities has been reported to be less with drugs with ISA, and the incidence of bronchospasm less with cardioselective drugs. In the management of uncomplicated mild-to-moderate hypertension, all beta blockers are equally effective and produce less troublesome side effects than alternative antihypertensive agents. For effective therapy beta blockers can be used in 2 divided daily doses or even once daily.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. Immobilization of TiO2 nanofibers on reduced graphene sheets: Novel strategy in electrospinning.

    PubMed

    Pant, Hem Raj; Adhikari, Surya Prasad; Pant, Bishweshwar; Joshi, Mahesh K; Kim, Han Joo; Park, Chan Hee; Kim, Cheol Sang

    2015-11-01

    A simple and efficient approach is developed to immobilize TiO2 nanofibers onto reduced graphene oxide (RGO) sheets. Here, TiO2 nanofiber-intercalated RGO sheets are readily produced by two-step procedure involving the use of electrospinning process to fabricate TiO2 precursor containing polymeric fibers on the surface of GO sheets, followed by simultaneous TiO2 nanofibers formation and GO reduction by calcinations. GO sheets deposited on the collector during electrospinning/electrospray can act as substrate on to which TiO2 precursor containing polymer nanof